How much menthol and camphor belongs in a balm, and who should avoid them

The US monograph caps camphor at 11 percent and menthol at 16 percent by use. Camphor ingestion of one to two grams can be fatal to a small child.

Menthol and camphor are the two materials in a balm most likely to produce a strong sensation, and the two most likely to cause real harm at the wrong dose, on the wrong skin or in the wrong person. Both sit inside named concentration bands in United States drug law, and both have a paediatric poisoning record that a label compresses into one line of small print. This page gives the numbers, the routes of exposure that turn an ordinary jar into a poisoning, and the people who should leave these materials alone.

• Camphor: 3 to 11% as a counterirritant
• Menthol: 1.25 to 16%
• Not on or near the face under 2
• Never on broken skin or mucosa

What these molecules do to a nerve, and what they do not do

Menthol binds TRPM8, the ion channel that reports cold. Open it and the nerve sends a cold signal whether or not the tissue temperature has changed, which is why a balm at skin temperature feels chilled. Camphor is less selective: it activates TRPV1, the receptor for noxious heat and capsaicin, and TRPV3, a warmth receptor abundant in keratinocytes, while inhibiting TRPM8 at higher concentrations. Repeated activation of TRPV1 desensitises it, which is the mechanism behind the warm-then-numb pattern people describe from a strong rub.

All of this is counter-irritation: a competing sensation generated in the skin that changes how a deeper ache is perceived. It is not an anti-inflammatory action. Nothing in the mechanism reduces swelling, repairs a strained muscle or opens a blocked nose, and the sensation is not a measure of anything happening in the tissue underneath. The receptor pharmacology is set out in more detail on menthol, camphor and similar actives. The practical consequence is that a stronger sensation is not better treatment, and chasing it by raising the percentage is the single most common way a homemade rub becomes unsafe. If your product stings rather than cools, the causes are worked through in balm stings or burns.

The concentration bands that carry legal weight

In the United States, a product sold to relieve muscular aches is a drug, not a cosmetic, and the relevant conditions sit in the topical analgesic, anaesthetic and antipruritic monograph, known as M017 and derived from the 1983 tentative final monograph that people still cite as 21 CFR Part 348. It sets two distinct sets of numbers, and confusing them is why quoted limits vary so wildly between sources. As a counterirritant, camphor runs 3 to 11 percent and menthol 1.25 to 16 percent. As a topical analgesic, anaesthetic or antipruritic, the same two materials are held far lower, camphor at 0.1 to 3 percent and menthol at 0.1 to 1 percent.

The monograph also sorts counterirritants into groups and only permits combinations that draw on more than one group, which is why the classic chest rub pairs camphor and menthol with a third material rather than simply doubling one of them. None of this is a cosmetic allowance. A balm that says it soothes aching muscles has made a drug claim in the US, and the difference is explained in cosmetic versus drug claims and in the US labelling rules covered in labelling cosmetics for the US.

Camphorated oil, and why old family recipes exceed the ceiling

Camphorated oil was a household staple: roughly 20 percent camphor dissolved in cottonseed oil, sold in a bottle that looked much like any other oil. Children drank it, adults confused it with castor oil and gave it by the spoon, and seizures followed. The US Food and Drug Administration acted in the early 1980s, and camphorated oil now appears among the over-the-counter products the agency does not regard as generally recognised as safe and effective, listed at 21 CFR 310.545.

That history matters because pre-1980 recipes circulate freely. A recipe calling for camphorated oil, or for a rub with camphor "to taste", or a doubled-up version made stronger because the shop-bought one felt weak, is not a more effective product. It is a product outside the band that regulators drew after counting poisonings. The workable versions, with percentages that stay inside the monograph, are in chest rub balm and muscle rub balm.

The paediatric numbers, and the arithmetic behind them

Camphor is absorbed rapidly from the gut and crosses into the central nervous system quickly. Seizures have been reported within about 5 to 90 minutes of ingestion, sometimes as the first sign, with no warning vomiting. The evidence-based out-of-hospital guideline published by the American Association of Poison Control Centers uses roughly 30 mg per kg of body weight as the threshold above which a child should be referred for assessment. Fatalities have been reported in young children after ingestions in the region of 1 to 2 g.

Those figures only become meaningful once you convert them into jars and spoonfuls.

A single teaspoon of an ordinary vapour rub takes a one year old most of the way to the referral threshold. A teaspoon of camphorated oil passes it three times over and lands inside the range where deaths have been reported. This is not a theoretical hazard: these products are kept in bedrooms and bathrooms, smell pleasant, and sit in wide-mouthed jars a toddler can get a fist into.

Under the nose, in the nostrils, and lipoid pneumonia

The habit of dabbing a vapour rub under a child's nose, or inside the nostrils, is where the label instruction and common practice diverge most sharply. A case published in 2009 described an 18 month old who developed severe respiratory distress after a rub was applied directly under her nose. The accompanying laboratory work by Abanses, Arima and Rubin, using a ferret trachea model, found that vapour rub increased mucin secretion and reduced ciliary beat frequency. In an airway already narrowed by infection, more secretion cleared more slowly is the wrong direction to move.

The second problem is the base rather than the actives. Petrolatum applied inside the nose can be aspirated in small quantities over time and cause exogenous lipoid pneumonia, which is documented for chronic nasal use of oily preparations in both children and older adults. Petrolatum is an excellent occlusive on intact skin, as covered in petrolatum and mineral oil, and a poor thing to inhale.

The rule that follows is simple and is what the manufacturers themselves print: camphor, menthol and eucalyptus preparations do not go on or near the face of a child under two, and never inside the nose at any age. Chest and back only, on intact skin, for children old enough. Menthol and peppermint carry a related caution in infants, where application near the nose or mouth has been associated with laryngospasm and apnoea, which is why peppermint oil is left out of anything intended for a baby. The wider set of rules is in balms for babies.

Methyl salicylate is a salicylate dose, not a scent

Wintergreen-scented rubs carry the highest systemic risk of anything in this category, and it is easy to miss because the material smells like sweets. Methyl salicylate is around 98 percent of oil of wintergreen, and 1 mL weighs roughly 1.2 g. A single 5 mL teaspoon of the oil is conventionally described as equivalent to about 7 g of aspirin, more than twenty adult tablets. Deaths from swallowing small volumes are documented in the toxicology literature, and case reports of systemic salicylate poisoning from heavy topical use exist as well.

Three groups should avoid it on the skin. Anyone taking warfarin or another anticoagulant, because published case reports describe raised INR and bleeding after topical methyl salicylate. Anyone with salicylate sensitivity or aspirin-exacerbated respiratory disease. And children or teenagers with a viral illness such as chickenpox or influenza, where salicylate exposure carries the Reye's syndrome caution that removed aspirin from paediatric use in the first place. Use in pregnancy needs a conversation with a midwife or doctor rather than a rule of thumb, and the general position is set out in balms in pregnancy.

Heat, occlusion and exercise raise a dose you did not choose

Percentage in the jar is only half of the exposure. The other half is how much of it crosses the skin, and that is not fixed. Work published in the European Journal of Clinical Pharmacology in 1986 by Danon and colleagues showed that exercise and heat exposure substantially increase percutaneous absorption of methyl salicylate compared with rest at normal temperature. Occlusion does the same: a tight bandage, cling film, a heat pad, or the simple fact of applying a rub and then getting into bed under a duvet all raise the fraction absorbed. Skin still hot and hydrated from a shower or sauna is more permeable again, for the same reasons set out in lipid penetration into skin.

In 2012 the FDA issued a safety communication about rare cases of serious burns, including second and third degree burns, after over-the-counter topical muscle and joint products containing menthol or methyl salicylate. Many involved higher-strength products, and a number followed the use of heat or a tight dressing over the application. In 2007 the death of a teenage runner in New York was attributed by the medical examiner to methyl salicylate toxicity associated with heavy use of a topical muscle product, a case that is widely reported rather than published as a clinical study, and which is best treated as a warning about repeated whole-limb application in someone exercising hard.

Where these materials never belong

Some exclusions are absolute rather than dose-dependent, because the tissue involved has no barrier worth speaking of or because the exposure cannot be controlled.

• Eyes and eyelids. Volatile menthol and camphor reach the eye from nearby skin as vapour, and direct contact is painful and potentially damaging.
• Mucous membranes. Inside the nose, mouth, genital or anal skin. Absorption is fast and unpredictable.
• Broken, abraded, sunburnt or freshly shaved skin. The stratum corneum is the rate-limiting barrier, and without it the dose is no longer the one you calculated.
• Fresh tattoos and post-procedure skin. Follow the artist's or clinician's instructions first; the reasoning is in balms and tattoo aftercare.
• Lip products for young children. A lip balm is eaten by definition, which is why cooling actives have no place in one, as set out in lip balm for children.
• Pets. Camphor and many essential oils are toxic to dogs and cats, who then groom the treated area. Nothing intended for human aches goes on an animal, and the alternatives are covered in balms for pets.

What applies outside the United States

The monograph numbers are American drug conditions and do not automatically apply anywhere else. In the EU and UK, menthol and camphor are permitted cosmetic ingredients with no numeric ceiling written into the Cosmetics Regulation, which means the safe level is whatever the responsible person's safety assessor concludes and signs for, product by product, as described in safety assessment and the CPSR. Making a decongestant or analgesic claim moves the product into medicines regulation instead, a line that matters for anyone selling, covered in selling balms in the UK and EU. Health Canada's Cosmetic Ingredient Hotlist restricts camphor specifically, so a Canadian seller should read the current entry rather than assume the US band applies.

For a small maker anywhere, the monograph bands are still the most useful reference points that exist, because they are the only published numbers derived from a regulator weighing efficacy against reported harm. Treat 11 percent camphor as a hard ceiling and stay well under it. A workable chest rub sits nearer 4 to 5 percent camphor and 2 to 3 percent menthol, which is where the commercial products have sat for decades.

The decision rule, and what this page cannot settle

Use the sensation as a comfort feature, not as a measure of dose. If you want the cooling, the lowest concentration that produces it is the right one, because the extra percentage buys sensation and toxicity in the same step and buys no additional pharmacology. Keep camphor at or below 5 percent in anything you make, keep menthol in the low single figures, avoid methyl salicylate entirely unless you have read the salicylate cautions above and none apply to the person using it, and treat under-two, broken skin, mucosa and pets as absolute exclusions rather than judgement calls. Essential oils that deliver these molecules indirectly count towards the same total, which is why the dilution arithmetic matters as much as the neat active does; run it through the essential oil dilution calculator rather than by eye.

What this page cannot do is tell you whether these materials are appropriate for a specific person. Counterirritants have modest and short-lived effects on perceived pain, weaker than the evidence base behind topical NSAIDs, and none of them treats the underlying problem. If pain, congestion or a skin reaction is the reason you are reaching for a rub, the question of whether a balm is the right tool at all deserves an answer from a clinician who can examine the person, not from a concentration table.

Reviewed and updated 6 September 2026. Spotted an error? Tell us and we will fix and log it.