I asked Dr. David Kahn, an expert in drug allergy at UT-Southwestern to respond to your question. Please see his response below.
Camphor oil is used as a perfumery ingredient in soaps, cosmetics, and deodorants. It may also be found in paints, varnishes, waxes, and insecticides as a masking agent for odors. There are a few case reports of patients having allergic contact dermatitis to different forms of camphor found in sunscreen, ear drops and even a report of contact dermatitis to Vicks Vapor Rub; though this may have been due to other essential oils, not necessarily camphor.
The patient you describe has symptoms more consistent with urticaria and angioedema and I am unaware of any similar cases that have been reported in the literature due to camphor but allergic reactions to menthol have been reported since the 1960’s including cases of anaphylaxis to menthol containing toothpastes. As pointed out, Vicks VapoRub does contain menthol and many Halls cough products also contain menthol and a case of urticaria and worsening asthma due to cherry flavored Halls Cough drops has been reported. While she can tolerate peppermint candies, not all menthol is made from peppermint. Thus it is possible that she may be allergic to menthol.
What is distinctly unusual is her reports of having systemic reactions to inhalation of a suspected allergen. While urticaria and even anaphylaxis have been reported from inhalation of allergens, this is quite rare and often difficult to confirm via challenge. While the prick test was negative to camphor and mint despite her history of exquisite sensitivity, this does not necessarily exclude an allergy to the camphor (or menthol). However caution is also needed in interpreting the results of her open challenge to the inhalation of camphor. While she did exhibit pruritus and localized erythema, these exact symptoms can be seen with placebo challenges. A positive blinded challenge where the patient is blinded to both the smell and taste of camphor or menthol would be required to definitively confirm this unusual sensitivity. The use of a nose clip and several fragrant oils (e.g. wintergreen, spearmint, etc.) as additional challenge/masking agents may be helpful in determining if she truly is having allergic reactions to the inhalation of camphor or menthol.
1. de Groot AC, van der Walle HB, Jagtman BA, Weyland JW. Contact allergy to 4-isopropyl-dibenzoylmethane and 3-(4'-methylbenzylidene) camphor in the sunscreen Eusolex 8021. Contact Dermatitis. 1987 May;16(5):249-54.
2. Stevenson OE, Finch TM. Allergic contact dermatitis from rectified camphor oil in Earex ear drops. Contact Dermatitis. 2003 Jul;49(1):51.
3. Noiles K, Pratt M. Contact dermatitis to Vicks VapoRub. Dermatitis. 2010 May-Jun;21(3):167-9.
4. Marlowe KF. Urticaria and asthma exacerbation after ingestion of menthol-containing lozenges. Am J Health Syst Pharm. 2003 Aug 15;60(16):1657-9.
Thank you for your question. I hope that this information is helpful to you and your patient.
Daniel Jackson, MD
Dr. David Kah