Chili pepper leads plant creams on evidence, and most others rest on small trials

Key takeaways

• The strongest capsaicin product in the U.S. is an 8% prescription patch that only a health professional may apply, while drugstore capsaicin rubs top out at 0.25%¹².
• A 2014 Cochrane review found that cayenne creams and plasters eased chronic low back pain better than placebo in three trials with 755 people, the strongest evidence for any rub it studied, though still only moderate quality³.
• The FDA does not approve cosmetics before they’re sold, but since a 2022 law, companies must report serious reactions to their products within 15 business days⁴⁵.
• In an Italian study of 2,661 patients, nearly half used plant-based skin products, and propolis, daisy-family extracts and tea tree oil were the plant allergens that turned up most often in patch tests¹⁴.
• Tea tree oil should never be swallowed, and the FDA says many CBD products it tested didn’t contain the amount of CBD their labels claimed⁸¹³.

The strongest chili-pepper product sold in the United States isn’t a hot sauce. It’s a skin patch so potent that only a health professional may put it on, wearing nitrile gloves, after numbing the skin first¹.

Each patch, sold as Qutenza, holds 179 milligrams of capsaicin, the compound that makes peppers burn¹. The FDA’s label warns of substantial pain during treatment and brief jumps in blood pressure¹.

A few aisles over, capsaicin creams sell without a prescription. Under the FDA’s rules for drugstore pain rubs, they can hold 0.025% to 0.25% capsaicin². By our math, the 8% patch is roughly 32 to 320 times as concentrated.

Same compound, very different products. That spread runs across the whole shelf of plant creams, gels and oils.

A few have solid evidence for narrow uses. Many rest on long tradition and a handful of small trials. Below, we look at how they sort out, and how to try one safely.

The label decides whether anyone checked the jar first

The law sorts skin products by what they’re meant to do. The FDA defines a cosmetic as something for cleansing, beautifying or changing how you look⁴. A drug is meant to treat or prevent disease or to affect how the body works⁴.

A product can be both. The FDA’s own example is an anti-dandruff shampoo: it cleans hair like a cosmetic and treats dandruff like a drug⁴. Claims such as reducing cellulite or restoring hair can turn a cream into a drug, whatever it’s made from⁴.

That distinction decides how much checking happens before sale:

• Prescription drugs, like the 8% capsaicin patch, come with FDA-approved labeling that spells out who may use them and how¹.
• Over-the-counter (OTC) drugs, like capsaicin rubs, must follow an FDA monograph, a rulebook that sets allowed ingredients, strengths, uses, warnings and directions².
• Cosmetics get no FDA review before they’re sold, except for some color additives⁴.

Until recently, the FDA’s cosmetics powers were thin. The FDA says its authority over cosmetics grew little between 1938 and 2022⁶. Then the Modernization of Cosmetics Regulation Act, or MoCRA, became law on December 29, 2022⁶.

Under MoCRA, the company named on the label must report serious adverse events to the FDA within 15 business days⁵. Makers must register their facilities and list their products with ingredients, and the FDA can now order a recall⁴.

The numbers moved fast. Under the old voluntary program, the FDA had 5,176 establishment registrations and 35,102 product listings⁶. By May 2026 it had more than 15,000 active facility registrations and more than 1 million product listings, and industry reports of adverse events had more than tripled⁶. At that point, the FDA was still gathering input for its manufacturing-practice rules⁶.

Capsaicin is the plant rub with the strongest record

The prescription patch has a narrow job. Its 2009 FDA label covers nerve pain that lingers after shingles, called postherpetic neuralgia¹. It stays on for 60 minutes and can be repeated no more often than every three months¹.

Drugstore capsaicin rubs have a broader, milder job. The FDA’s monograph allows them for temporary relief of minor muscle and joint aches, such as simple backache, arthritis, strains, bruises and sprains².

Does the low dose do anything? For back pain, the answer leans yes. In 2014, Cochrane, an international group that pools the best trials, reviewed herbal medicines for low back pain³. It found 14 trials with 2,050 adults³.

Cayenne, or Capsicum frutescens, stood out. In three trials with 755 people who had chronic back pain, each found cayenne creams or plasters did better than placebo, and the reviewers judged the benefit probable³. Cochrane’s plain-language summary calls cayenne the only herb with moderate-quality evidence³. That’s a middle grade, not a top one, so we rate low-dose capsaicin promising but early.

The limits matter. The trials lasted six weeks at most, so they say nothing about long-term use³. Side effects were mild and short-lived³.

Product and condition both matter: our guide to herbal preparation forms describes a hot-pepper extract gel that didn’t beat placebo for knee arthritis.

If you use an OTC capsaicin rub, the monograph’s directions are clear²:

• Apply it no more than 3 to 4 times a day, and don’t use it on children under 2.
• Keep it away from your eyes, and off wounds or damaged skin.
• Don’t wrap the area tightly.
• Stop and ask a doctor if the pain gets worse or lasts more than 7 days.

Aloe gel may help burns heal, and aloe latex is another matter

One aloe leaf can become three different products. There’s the clear gel inside, the latex from the leaf’s outer part, and the whole leaf crushed up, latex and all⁷.

On the skin, the gel has some support. The National Center for Complementary and Integrative Health (NCCIH), part of the NIH, says research in people suggests aloe gel on a burn may speed healing and ease the pain⁷.

Aloe is also sold for acne, psoriasis and skin damage from radiation treatment. NCCIH points to only small studies for those uses, and it found too little reliable evidence to judge aloe for eczema or diabetic foot ulcers⁷. Most people tolerate the gel well, but some report burning, itching, rash or eczema⁷.

Swallowing aloe is a different story. In 2002, the FDA required companies to take aloe latex out of OTC laxatives because no one had shown it was safe⁷.

NCCIH also notes cases of acute hepatitis, a liver inflammation, in people who took aloe leaf extracts by mouth for three weeks to five years⁷. A whole-leaf extract that hadn’t had its color compounds removed was linked to gut cancers in animal studies⁷. Any form of aloe taken by mouth may not be safe for people who are pregnant or nursing, NCCIH says⁷.

The gel on a minor burn is a reasonable comfort measure. A drink or pill made from the latex or whole leaf is not the same product.

Tea tree oil and witch hazel: long use, small trials

Tea tree oil. NCCIH’s fact sheet, updated in 2025, says only a little research hints that tea tree oil could help acne, and firmer evidence is needed⁸. For athlete’s foot it may help, though perhaps not as well as standard treatments⁸.

One older trial gives a sense of the trade-off. A 2000 systematic review described 124 people with mild to moderate acne who used either a 5% tea tree oil gel or a 5% benzoyl peroxide lotion⁹.

Benzoyl peroxide cleared inflamed pimples better, while the two worked about equally on non-inflamed spots⁹. But side effects were less common with tea tree oil: 44% of users versus 79%⁹.

Tea tree oil has two firm safety rules. First, never swallow it; NCCIH says that can cause confusion, unsteadiness, an inability to walk and coma⁸. If someone swallows it, call Poison Help at 1-800-222-1222, and call 911 if the person collapses, has a seizure, has trouble breathing or can’t be woken¹⁵.

Second, freshness matters. Redness and irritation are more likely with an old product or one that has sat in heat, light or open air⁸. Our article on lavender covers rare hormone-related reports involving lavender and tea tree products in children.

Witch hazel. Europe’s herbal medicines committee reviewed witch hazel, Hamamelis virginiana, in 2009. The traditional uses it accepted include easing minor skin inflammation and dryness, relieving the itching and burning of hemorrhoids, and soothing minor mouth and gum inflammation¹⁰.

That acceptance rests on long use, not proof. The committee’s report notes that little clinical trial data exist¹⁰. One placebo-controlled study of 30 volunteers measured a drop in skin temperature, not symptoms¹⁰.

Witch hazel can sting or burn briefly, and allergic reactions are very rare, the report says¹⁰. Europe took a fresh look at the leaf monograph recently: it called for new data in 2025 and published an addendum to its assessment in May 2026¹¹.

Comfrey, arnica and calendula: short trials and strict limits

Comfrey’s skin use has one notable trial behind it. In the Cochrane back-pain review, a single trial of 120 people found that a comfrey root ointment eased pain better than a placebo ointment over the short term³. Cochrane rated that evidence low quality³.

Across the whole review, the authors of eight trials had potential conflicts of interest, and four more trial authors left the question unanswered³.

Comfrey taken by mouth is a separate and serious matter. Our article on tradition and evidence explains how comfrey tea and pills were tied to liver damage and how regulators responded.

Arnica and calendula creams are covered in depth in our guide to herbal preparation forms, including its best arnica trial. Both plants belong to the daisy family, and daisy-family extracts were among the most common plant allergens in patch testing¹⁴.

CBD creams are legal cosmetics with an unknown dose

The FDA has approved exactly one CBD drug: Epidiolex, a prescription form of purified CBD for seizures from Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex in patients 1 and older¹².

Everything else sits in a gray zone. As of its July 2024 guidance, the FDA has concluded that CBD products can’t be sold as dietary supplements, and it bars adding CBD to food sold across state lines¹².

Cosmetics are looser. No cannabis-derived ingredient is specifically banned from cosmetics, but a product still can’t be harmful under normal use¹². And a CBD cream sold to relieve pain or treat a disease is making a drug claim⁴¹². The FDA has sent warning letters to companies claiming CBD prevents or treats serious diseases such as cancer¹².

Quality is a real question. In a 2020 consumer update, the FDA said it had tested some CBD products and found many didn’t contain the CBD levels they claimed¹³. It has also looked into reports of contaminants such as pesticides, heavy metals and THC¹³.

The biggest gap is basic. Among its open questions, the FDA lists how much CBD your skin absorbs from a cream¹³. Until someone measures that, any CBD lotion’s dose is a guess.

Skin reactions come with the plant’s chemistry

A plant can make compounds that irritate skin or that the immune system learns to attack. That second problem, an allergy, is called allergic contact dermatitis.

In 2014, researchers at several Italian centers reported on a questionnaire given to 2,661 patients¹⁴. Nearly half, 48%, used plant-based skin products, and 139 people, about 11%, said such a product had caused a skin reaction¹⁴.

Then the doctors patch-tested 122 of the people who’d had reactions, using a set of plant allergens. Patch testing places tiny amounts of suspected allergens on the skin to see which ones trigger a reaction. Sixteen percent reacted, most often to propolis, daisy-family extracts and tea tree oil¹⁴.

These were patients, not a cross-section of the public, so the percentages aren’t anyone’s personal odds. Still, the authors’ conclusion is plain: natural products can cause contact allergy¹⁴.

If a product causes a rash, redness or a burn, the FDA’s advice is to stop using it and contact your health care provider⁵. You can report the reaction through the FDA’s MedWatch form or by calling 1-888-SAFEFOOD (1-888-723-3366) and choosing option 4⁵.

The topical plant product table

Use this table to match a product to its best-supported job, rated on our four-level evidence scale.

Product	Best-supported use	Evidence	Main risk
Capsaicin 8% patch (prescription)	Nerve pain after shingles	Strong evidence (FDA approval rests on two 12-week controlled trials)1	Substantial pain during treatment; brief blood pressure rise1
Low-dose capsaicin or cayenne rub or plaster	Chronic low back pain; minor muscle and joint aches	Promising but early (three moderate-quality trials, 6 weeks at most)23	Burning; keep off eyes and broken skin; no tight wraps2
Aloe gel	Minor burns	Promising but early7	Occasional burning, itching or rash7
Aloe latex or whole leaf by mouth	Constipation	Evidence says no, or unsafe7	Cramps, diarrhea, hepatitis cases7
Tea tree oil gel (5%)	Mild to moderate acne	Promising but early89	Irritation, worse with old oil; toxic if swallowed8
Witch hazel	Minor skin irritation; hemorrhoid itching	Not enough evidence (traditional use)10	Brief stinging; rare allergy10
Comfrey root ointment	Short-term back pain	Promising but early (one trial)3	No long-term safety data3
CBD cream	Pain or skin conditions	Not enough evidence1213	Unknown dose; labels may be wrong13

Notice the pattern: the best-tested products are regulated as drugs, and every one here carries some skin risk, so the first-use check applies to all.

Respecting plants means respecting their strength

Natural-health traditions have long treated plants as medicine, and capsaicin shows why that respect is earned. The compound that gives garden peppers their heat is now a prescription drug that calls for gloves, numbing cream and a clinician.

The same respect cuts the other way. If a plant is strong enough to help, it’s strong enough to irritate, sensitize or poison when used the wrong way. Treating a tea tree bottle or a capsaicin tube like medicine, with a dose, a time limit and a plan to stop, is the natural-health value of caution in action.

Questions readers ask

The bottom line

Plant creams run from a tightly controlled prescription drug to cosmetics no one checked before sale. Capsaicin has the strongest record: the prescription patch is an FDA-approved drug, and low-dose rubs have the best, if still early, trial evidence of any plant rub for back pain. Aloe gel, tea tree oil and comfrey also have promising but early evidence for narrow uses, and witch hazel and CBD creams rest mostly on tradition and open questions.

Read the label to learn which kind of product you’re holding. Introduce one product at a time, stop at the first rash, never swallow a skin product, and report a bad reaction to the FDA.

Related reading

• Water, alcohol or oil: how an herb’s form changes what you get
• What centuries of traditional use can and can’t tell you
• Lavender is the best-studied sleep scent, though its trials can’t hide the smell
• Europe now names about 80 scent allergens, while U.S. labels can still say “fragrance”
• Most health products aren’t scams, but many just haven’t been proven

Sources

1. U.S. Food and Drug Administration. “Qutenza (capsaicin) 8% patch: Highlights of Prescribing Information.” NDA 22-395, revised November 2009. accessdata.fda.gov
2. U.S. Food and Drug Administration. “Over-the-Counter (OTC) Monograph M017: External Analgesic Drug Products for OTC Human Use.” Posted May 2, 2023. accessdata.fda.gov
3. Oltean H, Robbins C, van Tulder MW, Berman BM, Bombardier C, Gagnier JJ. “Herbal Medicine for Low-Back Pain.” Cochrane Database of Systematic Reviews, 2014 (CD004504.pub4). cochranelibrary.com
4. U.S. Food and Drug Administration. “Cosmetics & U.S. Law.” Content current as of August 17, 2026. fda.gov
5. U.S. Food and Drug Administration. “How to Report a Cosmetic Product Related Complaint.” Content current as of October 5, 2026. fda.gov
6. Kozlowski S. “How FDA is Implementing Landmark Cosmetics Legislation to Positively Impact Public Health.” FDA Voices, U.S. Food and Drug Administration, May 4, 2026. fda.gov
7. National Center for Complementary and Integrative Health. “Aloe Vera.” NCCIH, last updated February 2025. nccih.nih.gov
8. National Center for Complementary and Integrative Health. “Tea Tree Oil.” NCCIH, last updated April 2025. nccih.nih.gov
9. Centre for Reviews and Dissemination. Critical abstract of Ernst E, Huntley A. “Tea Tree Oil: A Systematic Review of Randomized Clinical Trials.” Forschende Komplementärmedizin, 2000. Database of Abstracts of Reviews of Effects, NCBI Bookshelf. ncbi.nlm.nih.gov
10. European Medicines Agency, Committee on Herbal Medicinal Products. “Assessment Report on Hamamelis virginiana L., cortex; Hamamelis virginiana L., folium; Hamamelis virginiana L., folium et cortex aut ramunculus destillatum.” EMA/HMPC/114585/2008, November 12, 2009. ema.europa.eu
11. European Medicines Agency. “Hamamelidis folium: Herbal Medicinal Product.” EMA, periodic review call for data April–June 2025; assessment report addendum published May 11, 2026. ema.europa.eu
12. U.S. Food and Drug Administration. “FDA Regulation of Cannabis and Cannabis-Derived Products, Including Cannabidiol (CBD).” Content current as of July 16, 2024. fda.gov
13. U.S. Food and Drug Administration. “What You Need to Know (And What We’re Working to Find Out) About Products Containing Cannabis or Cannabis-derived Compounds, Including CBD.” Consumer Update, content current as of March 5, 2020. fda.gov
14. Corazza M, Borghi A, Gallo R, et al. “Topical Botanically Derived Products: Use, Skin Reactions, and Usefulness of Patch Tests. A Multicentre Italian Study.” Contact Dermatitis, 2014;70(2):90-97 (University of Milan record). expertise.unimi.it
15. America’s Poison Centers. “Poison Help.” poisonhelp.org, accessed October 2026. poisonhelp.org