The skepticism regarding CBD and hemp has always been there. What can we say — they’re literally made of nugs! But that ends today. We’re on a mission to find the best CBD oil from the top brands. We’ll discuss everything, including their hemp source to potency, production, and packaging.
If anything, we’re not trying to talk up CBD oil. We were pretty skeptical ourselves about cannabinoids. It was only after we got to know the health benefits, uses, types, and started researching brands could we trust CBD oils for the first time!
Hopefully, by the end of this article, you might see CBD oil in a new light!
How We Came Up with This List?
Before we started writing, we did plenty of research about CBD oils. And after countless hours of research, we came up with a list of brands that you could trust.
Authentic lab reports, potency, purity, source, and extraction process were our top priorities when we made this list.
The final cut was made by brands that source hemp from organically grown hemp farms and extract CBD with supercritical CO2.
Best CBD Oil Reviews
Most of our recommended picks are non-GMO, gluten-free, and vegan. So, you can dive in headfirst and explore our handpicked CBD products.
- Charlotte’s Web
- Rya Organics
- Joy Organics
- CBD American Shaman
- Sol CBD
- Medterra’s CBD tinctures
- Receptra Naturals
- Green Roads
If you’re skeptical about CBD, or all essential oils in general, you should find Charlotte’s Web pretty interesting! The brand became the talk of the town for its incredible range of hemp-derived oils. And we can see why!
The hemp extracts that go into their CBD oils are potent, naturally sourced, and free of artificial gimmicks. You get plenty of options, including a starter pack, an AM/PM routine, the good-old Original, and a Maximum Strength.
All of these are full-spectrum CBD oils with various potencies. But, what does that mean for you? It means they contain extracts from not only the hemp leaves but also the flowers and stalks. Together, they provide more relief from anxiety, joint pain, MS, or any heart and lung condition you might have.
Our personal favorite is their 30ml bottle. It’s a little over a hundred bucks but should last about a month if taken twice a day. There are 60 milligrams of CBD per ml. So, in terms of potency, this CBD oil by Charlotte’s Web is in a league of its own!
- Comes with about 17 mg of CBD per 30ml. bottle
- Good for managing everyday stress
- Includes essential terpenes, omega 3 fatty acids, and flavonoids
- Also available in a zesty Lemon twist and Mint Chocolate flavors
- Natural olive oil infused tincture might taste bitter to some
Charlotte’s Web definitely went the extra mile with its oils — featuring full-spectrum CBD, Omega 3 fatty acids, and many more! Thanks to their rigorous quality checks, you can reap all the benefits of this oil at a reasonable price.
Can’t trust random CBD brands with your money? Then you’ll love Populum for its award-winning CBD oil. Populum here got featured in Allure, American Sleep Association, and Forbes!
At first, the brand caught our eye with their full-spectrum oil, that too in a tasty orange flavor. You can take this oil for everyday stress, arthritis, headache, and nausea. Unlike other natural remedies, CBD oils provide relief in a short time.
The Populum organic CBD oil is available in multiple potencies starting from 250mg. to 2000mg. in a 30ml. bottle. You may also try their 450mg hemp oil soft gel capsules. One capsule contains 15 milligrams of CBD, and there’s a discount going on right now!
- Gluten-free and vegan
- Sourced from USA-grown, non-GMO plants
- Contains up to 2000mg full-spectrum hemp seed oil
- Triple-tested for potency
- Orange blossom flavor might be too sweet
Populum has the most diverse range of CBD products- including oil, capsules, cold therapy hemp rubs, and skincare. They’re 100% vegan, non-GMO, and now available in great flavors. One bottle of Populum CBD oil is worth trying; it may help with your focus, muscle pain, stress, and insomnia.
This is a brand that serves up the best CBD oils and skincare. If you’re wondering what CBD can do for your skin, prepare to have your mind blown!
For starters, it may treat acne, pigmentation problems, and psoriasis. Combine a CBD product with Retinol, and you can have smooth, flawless skin well into your 50s.
What’s special about Rya Organics is that their entire skincare range is more than just standalone CBD oils. You get CBD-infused Retinol serums, overnight treatments, glow tonics, and a hydrating lip conditioner.
Nexus Relief is the best-selling CBD product from Rya Organics. It’s got full-spectrum, CO2 -extracted cannabinoids and a rare ingredient called Boswellia Sacra. Like CBD, it’s historically used for treating pain, stress, and sleeplessness.
- Sugar-free, soy-free, gluten-free
- Made with 100% organic ingredients
- Offers a good range of CBD oil products
- Extracted with CO2
- The brand is too focused on their skincare range
You can’t go wrong with the Rya Organics CBD oil. It will help you have a restful sleep so that you can stay energized tomorrow. Plus, all of their CBD products are vegan, gluten-free, and soy-free. They can kick-start your collagen production and hydrate your skin for a youthful glow.
When it comes to treating pain with cannabis, Joy Organics pulls out all the stops. Their CBD oil line is brimming with the best-in-class potency — now available in broad-spectrum and full spectrum options!
The brand safeguards the hemp quality at every stage of production. Joy Organics is one of the very few CBD oil brands with an entire line of organic, USDA-certified CBD tinctures.
Additionally, they source hemp from organic hemp farms in the USA. To maintain high standards in their CBD tinctures, Joy Organics only extracts healthy hemp flowers from the plants. As a result, there are no undesirable plant sediments in the natural, honey-colored oil.
Like your CBD tinctures without trace amounts of THC? No problem! Look at their 900mg to 2250 mg broad-spectrum oils. The tetrahydrocannabinol is completely removed with an organic chromatography process. Pretty cool, right?
- Fast-absorbing CBD oil for pain
- Broad-spectrum and full-spectrum options
- Carries up to 75 mg of CBD per serving
- No bitter aftertaste
- First-timers might have liked low to moderate potency oils
We like the brand’s dedication and transparency. Their third-party lab reports match the labels, showing the exact amount of CBD written on the bottle. You get up to 75mg per serving, and one tincture should last about four weeks.
CBD American Shaman
Extracted from pure, USA-grown hemp, this oil is a great source of cannabinoids. We discovered the brand only recently and were surprised to see a few face serums as well!
CBD American Shaman offers several tinctures, topical serums, water solubles, and more. They’re sourced fresh from non-GMO hemp plants and tested multiple times for potency.
There’s a 15ml starter pack and a 30ml regular bottle. We particularly liked the 30ml size because it came in a decent 30mg/mL strength. It’s great for first-time users of this oil.
But what makes CBD American Shaman stand out?
The fact that they make hemp teas, gummies, candies, capsules, topical treatments, and a THC-free oil for their customers. In fact, their hemp skincare range has everything starting from hemp body lotion, bath bombs to serums and eye creams.
Not a fan of the way hemp smells in general? You’re in luck because you have 11 flavors to choose from. These gluten-free tinctures can be taken directly or mixed with other liquids.
- 300mg per bottle of full-spectrum hemp oil
- Also available as soft gel capsules, edibles, and gummies
- Sourced from USA-grown organic hemp plant
- Gluten-free, terpene-rich formula
- Moderate potency levels
Oils from this CBD brand are gluten-free, potent, and rich in terpenes. You can pick your favorite flavor from 11 different options. They’re reasonably priced and come with a 30-day return policy.
The best CBD oils have one thing in common, and that is a high potency level. Oils from Sol CBD are not only potent but also fast-absorbing.
If you’re looking for an oil that takes little time to take effect, you’ll find many from this new brand!
We particularly liked their Advanced Liposomal Sleep Formula.
Other than pure hemp extracts, it includes Passion Flower, Valerian Root, Gaba, and 5-HTP. These six ingredients promote deep sleep for men and women.
The CBD product has a gentle calming effect and makes your body relaxed enough to sleep.
It’s not a sedative and won’t keep you drowsy the morning after. Taking this oil every day can regulate your sleep cycles. Especially the ones from Sol BD will work in full swing — thanks to the rich MCT oil!
- Pure, CO2 -extracted formula for maximum potency
- Organically grown in the USA
- Chemical and solvent-free tinctures
- Doesn’t require a prescription
- A one-time purchase is quite expensive
In terms of potency and quality, Sol CBD doesn’t disappoint. We like the fact that they infuse a couple more natural ingredients in their Liposomal CPD formula. Their pure, full-spectrum oil in natural flavor is also potent and priced reasonably.
Can CBD really take you off the insomnia train?
Yes, it can! In fact, a full-spectrum CBD oil from CBDistillery will help you have the best sleep in a while.
We recommend this popular brand for its high-quality, non-GMO hemp. Presently, we can show you three reasons why we think you should give their CBD oil a shot!
First, you get high concentrations of CBD at an affordable price. They’re full-spectrum, so you get an entourage effect. It means cannabinoids will generally work better in the presence of similar hemp-derived ingredients.
Up next, we have their highly concentrated tinctures starting from five hundred milligrams per bottle.
2500mg/30ml is as high as CBDistillery will go.
We can’t help but mention their Extra Strength CBN + CBD Sleep Tincture. Featuring 300mg CBN and 900mg CBD content, this is the best sleep tincture money can buy!
- Contains about 30 servings in a bottle
- Full-spectrum tinctures for your overall well-being
- Made of non-GMO cannabis plant
- Promotes restful sleep
- Comes only in mild CBD concentrations
CBDistillery tinctures are US Hemp Authority certified. We can say with certainty that their 500mg CBD is worth trying. Overall, we’ll get this oil for treating moderate symptoms.
Medterra’s CBD tinctures
Having a hard time trusting those overpriced hemp oils? Then these CBD tinctures from Medterra will definitely get the ball rolling.
Medterra makes highly-concentrated CBD oils for MS, migraine, and stress relief.
We recommend Medterra to people with chronic pain and arthritis. And the reason is their oils are available from 500mg to 3000mg strengths. On top of that, you get coconut MCT oil as the carrier oil.
The thing is — oils work faster when they’re paired with essential fatty acids. And MCT oil happens to be an excellent team player! It makes sure that the CBD extracts are quickly absorbed into your system.
We’d choose the 3000mg bottle if we were you! It’s THC-free, citrus-flavored, and the most potent oil in its CBD range.
- 99.6% CBD content with coconut-derived MCT
- Extracted with supercritical CO2
- 500mg to 3000mg CBD per bottle
- Also available as THC-free, broad-spectrum hemp oil
- May contain higher CBD content than the specified potency
Thanks to the addition of MCT oil, your body can now absorb Medterra CBD much faster. Even the lowest, 500mg CBD tincture from this brand, is significantly effective if you have arthritis or insomnia.
Be it broad-spectrum CBD products or body cream, cbdMD is the first brand in the CBD industry to start it all. They have an impressive range of CBD oil tinctures, balms, bath salts, and massage oils.
Are you in your 20’s with back pain like an older man? Here’s what you’re doing wrong-
You completely dismissed the idea of taking CBD oil, an age-old natural remedy for stress.
So, if you like to start with something other than oil, you’ll find gummies, body lotions, and sleep aids right on the cbdMD website.
We can’t recommend the cbdMD oil enough. If you liked Medterra’s CBD products and found them a bit pricey, you should put your foot down on cbdMD. They both have MCT oil better absorption.
Finally, the brand is one of the very few CBD companies that manufacture 1500mg, 60ml bottles in four flavors!
- A GMP-certified broad-spectrum oil
- Includes MCT oil for better bio-availability
- Now available in 60ml value packs
- Zero THC formula
- Synthetic flavored oils
It’s a budget-friendly CBD tincture with 1000mg to 1500mg cannabinoids, terpenes, and MCT. We suggest it for anyone who likes THC-free, broad-spectrum products with zero artificial additives.
Receptra Naturals is pulling ahead in their hemp game with this brand-new CBD oil. Recently, they’ve added a powerful remedy containing 66mg of CBD in a handsome 30ml bottle.
All CBD tinctures contain organic hemp seed oil in different concentrations.
Then you must be thinking — why should I buy CBD from Receptra Naturals? For one, they contain avocado, MCT oil, turmeric, omega 3, and omega 6 fatty acids apart from hemp extract.
This rich infusion can bring a positive impact on your metabolism and sleep quality. Not to mention, it will also relieve post-workout muscle pain for gym rats!
Receptra Naturals has an alternative hemp balm with a 400mg CBD content and Arnica.
In any case, it’s worth a try than those sticky white pain-relief rubs. You won’t feel any instant cooling effect, though. But your sleep quality will significantly improve with the Receptra Naturals CBD oil.
- Treats sleeplessness and anxiety
- Relieves post-workout muscle pain
- Infused with avocado, MCT, turmeric, omega 3 and omega 6 fatty acids
- Also available as topical balms and body creams
- Cold ethanol extraction is not the ideal way to extract CBD
This CBD product by Receptra Naturals is good quality for sure. However, the fact that their hemp is extracted using ethanol is a let-down for us.
So, you’re down with a sports injury and not being able to sleep. If only there were something to make you feel better! Well, guess what? There is!
CBD products from Green Roads are powerful, straightforward, and high in potency. They have a full-spectrum oil with trace amounts of THC for quick relief from pain.
We like how Green Roads labeled their oils in Mild, Moderate, and Mighty categories. You know what they say- start small and build up as you go!
Although, unless you absolutely need it for anxiety or chronic pain, you shouldn’t take the 2500mg/ 30mL CBD right away. We’re sure it applies to all oils with hemp extract!
- Gluten-free and vegan CBD formula
- Available in many strengths up to 1500mg
- Tastes natural and smells of terpene
- Independent lab tested
- A few products use synthetic flavorings
Other than the full-spectrum hemp oil, we also liked the broad-spectrum CBD product line from Green Roads. They come in lots of different flavors and Rip n’ Sip sachets for sound sleep.
CBDFx is a cruelty-free brand working with cannabinoids for your everyday wellness.
First of all, these oils are one-hundred-percent vegan and organic.
It gives us joy to finally say this — these oils are universally vegan, rich with pure cannabinoids, and the most bioavailable in their class.
CBDFx infuses its tinctures with Curcumin and Coenzyme Q10 — two powerful, naturally-occurring cannabinoids for pain relief.
Their CBD+ CBN calming tincture is a personal favorite. It contains relaxing terpenes and is now available in 500mg Regular, 1000mg Extra Strength, 2000mg Maximum Strength, and 4000mg Maximum Strength Plus.
- Cruelly-free, organic, and vegan
- Made of terpene-rich USA-grown hemp plant
- Carries up to 4000mg of CBD in a 30ml packaging
- A bioavailable CBD product for better absorption
- Calming CBD tincture might not relieve extreme symptoms
CBDFx oils are cruelty-free, organic, and vegan. They include Curcumin and Coenzyme Q10s with less than 0.3% THC. But if you don’t want anything to do with THC at the beginner stage, you’ll love their 0.01% broad-spectrum oils.
Featuring organic Colorado-grown hemp extract, CBDPure offers some of the best CBD oil tinctures for the price.
We’re sure you’ll agree with us when we say this:
Falling asleep with bad joint pain is really hard!
No matter how much you toss and turn, you just can’t sleep a wink. If this is something you can relate to, then the CBDPure CBD oil is a must-have.
It’s a full-spectrum, CO2 -extracted CBD oil with high levels of bioavailability. The hemp plants are grown in Colorado and Washington soil by local family farmers.
The oils are completely free of artificial additives and fillers.
Currently, they make CBD products in 300mg to 1000mg concentrations. A pinch of this high-quality CBD oil goes a long way.
- Sourced from Washington and Colorado-grown organic hemp plants
- 100% CO2 -extracted CBD for maximum strength
- Full-spectrum oils up to 1000mg
- Also available in 60ml bottles
- Fewer products to choose from
We believe the Full-spectrum CBD from CBDPure has an edge when it comes to quality. It’s one of the most potent CBD oils out there! So, you should start with a small amount.
What to Look for Before Buying CBD Oil
Full-spectrum CBD oils may contain small amounts of THC — the main psychoactive agent that helps Gen Z get high.
To ensure you’re not getting anything undesirable in your system, you need to have a basic idea of cannabinoids.
Don’t worry. We’ve rounded up the top 5 things to consider before you buy CBD oil for the first time!
Trustworthy Hemp Source
If you recently saw your neighborhood teenager getting busted for growing cannabis in their backyard, don’t worry.
Your CBD oil is definitely not coming from that!
The pricey hemp oils you see online are usually sourced from industrial or organic hemp farms across the USA. You can trace back the best-tasting CBD oil from sunny Colorado.
USDA organic certified brands like Joy Organics are great places to look for CBD oil!
There’s nothing better than CO2 -extracted CBD.
And the reason for that is— CO2 extraction is by far the cleanest way to extract pure CBD oil from hemp plants. No chemical solvents are used in this process as opposed to the traditional cold ethanol extraction.
Types of CBD Oil
CBD oils usually come in three different types depending on their THC content and association with other cannabinoids.
Full Spectrum CBD
A full-spectrum organic oil captures the natural properties of an entire plant. We’re talking flowers, leaves, stalks, and whole plant extracts. They may or may not be infused with other cannabinoids. And there’s a tad amount of THC (0.3% or less).
We always felt that Curcumin and Coenzyme Q10 make ordinary CBD oils much better. The latter is an all-natural antioxidant. Your body produces it for energy.
As you age, your energy levels start to reduce. Coenzyme Q10 can supplement them, and you may just find one at CBDFx.
Broad Spectrum CBD
Some people don’t like THC. It’s as simple as that. But, it turns out — cannabinoids alone can do a pretty good job! So, a broad-spectrum CBD oil is one without tetrahydrocannabinol or THC.
Brands that specialize in making THC-free CBD remove this element with a chromatography process. The product is totally safe and potent, like full-spectrum oils.
These products contain pure CBD without additional cannabinoids and THC. If you want to have the taste and feel of natural cannabinoids, CBD Isolates are the way to go!
Studies have found that they have great anti-inflammatory properties. You can mix CBD oil with your face cream to treat acne and inflammations.
The strength or potency of CBD oil is usually specified as x mg/ml or x mg. per serving. Most brands these days label the total potency of their CBD products for the full bottle.
For example, you’ll get approximately 30 milligrams of CBD per serving from a 900mg, 30ml bottle.
We’ll suggest a mild 25mg dose for first-time users. It’s enough to help you relax after a day’s work. However, chronic muscle pain from sports calls for a higher dosage. In any case, stay below the 60mg line for the first month.
The potency of cannabinoids may also depend on how they were extracted. So, CO2 extraction is your best bet to ensure the highest possible strength.
A high-quality CBD oil will come in a sturdy, tinted bottle with a dropper. It should also come with easy-to-follow directions.
The most important part of CBD packaging has got to be the dropper.
Note that when they say “take a full dropper of CBD oil morning and night,” they do not mean you fill it all the way to the rubber cap. Keep it half full, and there you get the accurate dosage of CBD!
Independent Lab Tests
Third-party lab tests are there to see if the brands’ claims check out for real. Also, they verify organic farming methods, product standards, potency, and side effects.
So, before you buy any CBD item, take two minutes to check those lab reports. They should be listed on the website.
Difference Between CBD Oil and Hempseed Oil
Hempseed oils are pretty self-explanatory. They are collected from only the seeds of a cannabis plant. The Cannabis Sativa- to be specific.
On the other hand, CBD can be extracted from both the Cannabis Sativa plant and the Cannabis Indica plant.
Cannabis Indica is illegal in a couple of states as we speak. Therefore, 9 out of 10 times, CBD is extracted from Cannabis Sativa.
It’s nearly impossible to tell which one is better; it depends on which one you need more as a medical requirement.
For example, CBD is better for pain and inflammation treatment. Hempseed oil is much better for the skin. Although it doesn’t contain the tetrahydrocannabinol or relaxing properties like CBD does.
The ball is in your court. Pick that that covers your needs!
How to Use CBD Oils and Tinctures?
Users of this life-changing oil have shown significant improvement in their immune system, energy, and overall health. A good-quality CBD oil tincture can give you plenty of health benefits.
But first, you need to know how to take cannabinoids safely!
A CBD oil tincture is meant to be taken sublingually (under the tongue) and kept for 20 seconds. Try not to drink water in the first minute, and you’re good to go!
CBD extracted from the Cannabis plant is powerful, but it works twice as well when using MCT coconut oil as a carrier oil.
Keep your CBD consumption 15 to 40 milligrams for mild to moderate pain. From there, you can build up to a dose that safely and efficiently relieves your symptoms.
Sportsmen, however, may be taking CBD in more powerful concentrations.
Usually, 40 to 60 mg of CBD is considered a safe range for people who specifically take CBD for pain.
Consult your doctor if you have taken full or broad-spectrum CBD oils more than the recommended amount.
The Benefits of CBD Oil
If you were recently looking at a health and wellness website, chances are — that deal on Mint Chocolate CBD oil caught your attention.
You might have friends who take CBD oil for pain. But did you know that CBD extract promotes acne-free skin at the same time?
People with high blood pressure and anxiety also benefit from the neuroprotective factors of cannabinoids.
Let’s look at the benefits of CBD at a glance, shall we?
- Alleviates anxiety and stress
- Naturally lowers high blood pressure
- Regulates your sleep cycles for deep sleep
- Soothes inflammation in your skin and body
- Boosts your skin’s natural collagen production for a better appearance
- Relieves painful symptoms caused by sports, spinal cord injuries, chronic pain, and arthritis
- May relieve several neurodegenerative disorders such as MS, Alzheimer’s, Parkinson’s disease, and stroke
- According to NCI, cannabinoids may alleviate the side effects of cancer treatments
Side Effects of CBD Oil
Got your eye on a gluten-free CBD oil tincture? You may as well know the side effects of CBD now.
Here’s what CBD oil companies will never tell you!
Just like every other natural remedy, CBD has a few drawbacks of its own. They might occur with extremely high doses of cannabinoids in the long term.
Mood changes, loss of appetite, gastrointestinal problems are associated with a wide range of products.
What we found the most alarming is that the top CBD oils and tinctures, in high concentrations, could be potentially risky for liver patients.
And there’s a possibility of losing fertility for men.
They might interact with your prescription medications to some extent. It’s not a well-researched topic, so CBD products are yet to receive FDA approval.
Anyhow, the health benefits of CBD outweigh these side reactions.
Frequently Asked Questions
Is CBD oil good for relieving back pain?
Even though CBD oil and its usage are still being studied, various researches have come with positive results- that CBD oil can actually help relieve back pain. It helps reduce inflammation and can be used to combat anxiety. Moreover, CBD oil helps a patient relax and have a good sleep which is key to recover from back pain.
Is CBD oil good for your skin?
CBD oil can be very effective against the likes of eczema, psoriasis, and dermatitis. It’s because of the anti-inflammatory properties that the oil possesses. Apart from that, it can reduce irritation and soothe your skin. CBD oil is particularly good for sensitive skin.
Which Full-Spectrum CBD is the best?
Made from USA-grown hemp, the full-spectrum CBD oil by CBDistillery is considered the best. It alleviates arthritis, relieves stress, and promotes a good night’s sleep. Moreover, hemp is collected from organic plants and extracted with supercritical CO2.
Is CBD oil better than hemp seed oil?
Hemp seed oil and CBD oil are quite different in their production. While CBD oil is extracted from the leaves, flowers, and stalks, hemp seed oil is collected from the seeds.
How to take CBD oil every day?
CBD oil is used and consumed in various ways all over the world. You can rub it on the inflammatory areas of your body, or you can drink it with a cocktail, coffee, or a smoothie. If you prefer to use it as a salad dressing or have it as a capsule, you can do that as well!
Why do some CBD oils contain MCT?
MCT oil ensures that your body gets the most out of the CBD oil you’re consuming. It carries the oil directly to your bloodstream. This results in your body absorbing a greater concentration of CBD and thereby getting a better result.
CBD oil is definitely not a cure-all.
But its natural healing properties can fight arthritis, heal injuries fast and provide relief against a wide range of symptoms.
Here is where you can find all of the brands mentioned in our list:
- Charlotte’s Web (here)
- Populum (here)
- Rya Organics (here)
- Joy Organics (here)
- CBD American Shaman (here)
- Sol CBD (here)
- CBDistillery (here)
- Medterra’s CBD tinctures (here)
- cbdMD (here)
- Receptra Naturals (here)
- Green Roads (here)
- CBDFx (here)
- CBDPure (here)
Now, the best CBD oil has got to be from Populum, CBD American Shaman, or CBDistillery. These particular brands met all our standards and more!
The links contained in this product review may result in a small commission if you opt to purchase the product recommended at no additional cost to you. This goes towards supporting our research and editorial team and please know we only recommend high quality products.
Please understand that any advice or guidelines revealed here are not even remotely a substitute for sound medical advice from a licensed healthcare provider. Make sure to consult with a professional physician before making any purchasing decision if you use medications or have concerns following the review details shared above. Individual results may vary as the statements made regarding these products have not been evaluated by the Food and Drug Administration. The efficacy of these products has not been confirmed by FDA-approved research. These products are not intended to diagnose, treat, cure or prevent any disease.