Allergic Contact Dermatitis

A 42-year-old man presented with a 1-year history of progressively worsening dermatitis. The patient worked as an air conditioning installer and participated in multiple outdoor recreational activities.

Physical examination. On exam, ill-defined red scaling patches were noted on the lower legs and dorsal feet, with lesser involvement of the palms and several dorsal fingers. The rash was pruritic and worse in the heat. Treatment had included intramuscular injection of corticosteroids, topical clobetasol 0.05% ointment, and emollients. This treatment did help to improve the rash, but did not resolve the rash.

Laboratory tests. Due to a suspicion for allergic contact dermatitis, the patient was referred for patch testing. A reading was performed at 72 hours.

Diagnosis. The patient had several reactions, including a notable reaction to potassium dichromate. Potassium dichromate is used in the tanning of leather, and is therefore found in many different leather objects. Upon questioning, the patient reported frequent use of leather boots and occasional use of leather gloves when outdoors or at work. He was counseled on avoidance, and advised to use polyvinyl chloride boots and white cotton and vinyl gloves instead.

Discussion. Allergy to leather boots and gloves typically results in chronic recurrent dermatitis of the feet, lower legs, dorsal hands, and palms.¹ This type of allergy, known as allergic contact dermatitis (ACD), is mediated by T-cells and is also known as type 4 delayed-type hypersensitivity. When an allergen contacts the skin, it triggers inflammation in that local area, typically days later.

The delay in appearance of the rash is a hallmark of ACD. In fact, this delay is the reason why many patients are unable to identify the specific cause of the rash. First exposure to the allergen initiates the formation of memory T- cells, which cause a reaction upon subsequent exposure to the same allergen.² The reaction can occur up to 1 week following exposure, though typically occurs between 48 to 72 hours post-exposure.²

Potassium dichromate is a relatively common allergen in patients undergoing patch testing in the United States and Canada.³ This chemical is used in the tanning of leather and is found in almost all types of leather objects.⁴ Patients frequently present with foot or lower leg dermatitis resulting from leather shoes and boots, while dorsal hand or palmar dermatitis may result from leather gloves. Reactions have occurred on the back or posterior thighs following contact with leather upholstery.

As sweat increases leaching of this chemical from an object, reactions tend to be worse when in the summer months. Contact dermatitis is also worse at areas where there is increased friction of the object against the skin, as in snug gloves or shoes.

Since potassium dichromate imparts a green color, it is also found in some green pigments used in paint, makeup, and tattoo inks.² It can also be found in wet cement, plywood, and metal plates.² Its presence in these products can pose specific hazards to certain occupations, such as construction and welding, where it may result in hand involvement. This is thought to be more prevalent in men, and once present, hand dermatitis from chromate allergy can last for years, even when exposure to the triggering allergen is removed.⁵

The diagnosis of ACD is made by patch testing, in which allergens are deposited in a chamber, fixed to the patient’s back and read after 72 or 96 hours. Once the allergen is identified, the mainstay of treatment is avoidance of the inciting substance. Many alternatives to tanned leather shoes exist. Some companies now sell vegan shoes, with no leather components. Leather that has been tanned with vegetable dyes is another option, although can be difficult to locate.²

References:

1.Landeck L, Uter W, John SM. Patch test characteristics of patients referred for suspected contact allergy of the feet-retrospective 10-year cross-sectional study of the IVDK data. Contact Dermatitis. 2012;66(5):271-278. 

2.Scheman A, Jacob S, Zirwas M, et al. Contact Allergy: alternatives for the 2007 North American contact dermatitis group (NACDG) Standard Screening Tray. Dis Mon. 2008;54(1-2):7-156.

3.Warshaw EM, Belsito DV, Taylor JS, et al. North American contact dermatitis group patch test results: 2009 to 2010. Dermatitis. 2013;24(2):50-59.

4.Thyssen JP, Jensen P, Carlsen BC, et al. The prevalence of chromium allergy in Denmark is currently increasing as a result of leather exposure. Br J Dermatol. 2009;161(6):1288-1293.

5.Fisher AA. Cement injuries: Part I. Cement hand dermatitis resulting in “chrome cripples.” Cutis. 1998;61(2):64.