Aluminum can cause allergic contact dermatitis: Allergen of the Year 2022
By Christen Mowad, MD, FAAD
June 15, 2022
Vol. 4, No. 24
Allergen of the year is an eagerly awaited award for those of us excited by allergic contact dermatitis. It has been given each year for over 20 years to highlight allergens of new and emerging significance and sometimes to highlight allergens that are notably not significant such as thimerosal and parabens. This year the honor goes to aluminum. (1)
Aluminum is ubiquitous and we are all exposed daily; however, aluminum and aluminum salts such as aluminum sulfate, aluminum acetate, and aluminum chloride hexahydrate infrequently cause allergic contact dermatitis. (2) One study estimates that 0.9% of adults and 5.1% of children are allergic to aluminum. (3) Aluminum is an allergen not commonly tested to in most patch test clinics and is not included in the three panels of the FDA-approved allergy patch test series. Allergy is sometimes incidentally picked up with reactions to the Finn chambers used in patch testing that are made of aluminum. Aluminum and its salts are present in many consumer products such as antiperspirants, toothpastes, and sunscreens, as well as foods, vaccines, tattoos, dental restorations, and in the transport, packaging, and construction industries. (1,2)
The most common clinical presentations are a nodular reaction at a site of vaccination or an eczematous reaction often in the axillary vault due to antiperspirant exposure. (1,2) The nodular reaction to the vaccine is felt to be a type IV hypersensitivity reaction. This can be treated with topicals or intralesional steroids. The axillary dermatitis can also be managed with avoidance of aluminum containing antiperspirants; it has been reported to occur with frequencies of 0.35-1.18% and can last 18-49 months. (2) Experts agree that the small risk of nodules occurring after vaccination is not a reason to forgo the vaccine and the benefits of disease prevention. (2)
Patch testing should be performed with aluminum chloride hexahydrate (ACH) 10% in petrolatum. This detects more aluminum allergy than ACH 2%. The exception is in children strongly suspected of aluminum allergy; then the 2% preparation can be used. A delayed patch test read performed at 1 week should be conducted to avoid missing 15-20% of aluminum allergies. (1-3) Finn chambers are made of aluminum but only rarely detect aluminum allergy. It is reported that aluminum allergy can vary over time so clinicians should consider retesting over time to avoid false-negative patch test reactions. (1,3)
Aluminum sensitization can occur with aluminum-containing preparations used for allergen-specific immunotherapy, also known as ASIT. Aluminum-containing vaccines are also a source of sensitization in addition to antiperspirants and astringents. (1) Aluminum is found in many vaccines and is felt to enhance the immune response to vaccinations by a depot effect and by activating antigen-presenting cells. (2) Aluminum adjuvants are in hep A, hep B, DTaP, pneumococcal and HPV vaccines to name a few.
Studies have shown that aluminum allergy is more common in children and in both children and adults with atopic dermatitis. (1-3) Even though there is widespread exposure to aluminum there is a low incidence of allergic contact dermatitis reported. This may be in part due to the limited patch testing that occurs for this potential allergen. We should keep aluminum in mind when approaching patients with reactions that could be consistent with aluminum allergy.
Point to Remember: Aluminum is the 2022 allergen of the year. Dermatologists should consider a contact allergy to aluminum, especially when observing an eczematous reaction in the axillary vault due to aluminum-containing antiperspirants or noting a nodular reaction at a vaccination site.
Our editor’s viewpoint
Warren R. Heymann, MD, FAAD
Admittedly, I am no contact dermatitis aficionado. Rather than offer a banal commentary, I prefer to use this section to ask Dr. Mowad some specific questions.
Is there any value of performing a use test with an antiperspirant on another site (such as the forearm)?
Dr. Mowad: Use testing can be helpful to determine if the product in question is causing an allergic contact dermatitis. It can be very useful when patch testing is difficult for the patient to complete given distance, time, cost, or lack of patch testing capabilities. The dermatologist should explain to the patient that use testing may demonstrate the product as causative but does not identify the individual allergen and therefore education and recommendation of safe products is not possible. Patch testing remains the criterion standard for detecting allergic contact dermatitis but there is a place for use testing in the right circumstance.
Does axillary dermatitis typically present when patients first start using aluminum deodorant or can it occur after years of use?
Dr. Mowad: Allergic contact dermatitis from a reaction to aluminum in antiperspirants can occur any time after sensitization so this can be early on or later in exposure.
There are other options for treating axillary hyperhidrosis, such as topical or oral glycopyrrolate, botulinum toxins, and iontophoresis. If a patient has no interest in these options and is proven to be aluminum-allergic, what topical antiperspirants do you recommend?
Dr. Mowad: There are many aluminum-free antiperspirants available over the counter and found in the Contact Allergen Management Program (CAMP) Database available on the Contact Dermatitis website. Reference 2 also lists many aluminum-free deodorants such as Secret aluminum free, Toms of Maine, Old Spice, and Dove to name a few.
I reflexively think of cinnamates as the culprit for toothpaste allergy; I never even knew about aluminum in toothpaste. Apparently, aluminum is used to prevent toothpaste from becoming too acidic. It may also be included as a colorant due to its white color. Do most toothpastes contain aluminum? Have you ever encountered an aluminum contact dermatitis to toothpaste in your practice?
Dr. Mowad: I have not encountered a patient allergic to aluminum found in toothpaste in my practice. However, many of us are not routinely testing to aluminum so we may be missing it. I think with the allergen of the year being aluminum and more attention being given to this allergen there will be more testing and perhaps more identification of this allergen. Aluminum exposure is common but aluminum allergy is currently not common. I think there is more to be learned about aluminum allergy as more of us perform testing with it.
Are there any cross-reactions of aluminum with other metals that dermatologists should be aware of?
Dr. Mowad: We do not usually see cross-reactions with chemically dissimilar structures. One concern may be metals that individuals are exposed to in similar products. So if there are products containing aluminum and other metals then potentially we could see co-reactions. As aluminum is not routinely tested for currently we will need more information which may be forthcoming as more individuals consider patch testing with the 2022 Allergen of the Year.
Bruz, M, Netterlid E, Siemund I. Aluminum- Allergen of the Year 2022. Dermatitis 33(1): 10-15, 2022.
Kulberg SA, Ward JM, Liou LL, Atwater AR et al. Cutaneous reactions to aluminum. Dermatitis 31(6):335-349, 2020.
Siemund I, Dahlin J, Hindsen M, SImerson E et al. Contact allergy to two aluminum salts in consecutively patch-tested dermatitis patients. Dermatitis 33(1): 31-35, 2022.
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