Preservatives
Sulfites
These compounds are preservatives found in cosmetics, hair dyes, and certain foods. Systemic contact dermatitis caused by sulfites in food has been described in numerous patients. One unfortunate vacationer developed axillary and groin dermatitis after ingesting large amounts of grapes, wine, shrimp, and french fries while vacationing in Italy.19 Among dietary sources, beer and wine contain higher levels of sulfites. Sulfites also can be found in some pickled foods; bottled citrus juice; dried fruits; and commercial prepared foods, such as powdered potatoes and gravy mixes. Other reports of SCD from sulfites include an enema preparation20 and anesthetics21 as the source of the allergen.
Formaldehyde
Formaldehyde can cause SCD after ingestion of aspartame, which is hydrolyzed to phenylalanine, aspartic acid, and aspartic acid methyl ester in the intestine.22 The methyl ester is converted to methyl alcohol, which is transported to the liver and oxidized to formaldehyde, which is then converted to formic acid. Hill and Belsito22 reported a case of SCD presenting as eyelid dermatitis after ingestion of an aspartame-based artificial sweetener. A similar case of eyelid, neck, and leg dermatitis was reported after ingestion of drinks and candy sweetened with aspartame.23
Parabens
Although parabens are rare contact sensitizers, there are a few reports of paraben SCD. Cases include a predominantly flexural pattern from ingestion of a mucolytic-containing methylparaben,24 a generalized eczematous eruption after intramuscular injection of ampicillin preserved with methylparaben and propylparaben,25 and diffuse dermatitis from methylparaben in a local anesthetic.26
Sorbic Acid
Sorbic acid is utilized as a preservative in foods and occurs naturally in red fruit, such as strawberries and cranberries.27 It is a rare allergen, but several cases of sorbic acid SCD have been reported, including perianal and buttock dermatitis,27 hand dermatitis in an infant,28 and hand-and-foot dermatitis in a storekeeper.29
Carmine
Carmine, or cochineal extract, is a red dye derived from dried pulverized scale insects of the family Coccidae. This chemical can be used in a multitude of foods and medications, including candies, yogurt, red velvet items, popsicles, food coloring, frozen meat and fish, ice cream, syrups, ketchup, sausage, donuts, cake pops, applesauce, canned fruits, soups, and drinks.30 Machler and Jacob31 described a child with recurrent episodes of erythroderma and periorbital edema in whom patch testing revealed a reaction to carmine. The patient’s mother connected the flares with ingestion of red velvet cupcakes.31 Ferris et al32 reported a likely case of SCD attributed to carmine in a multivitamin.
Steroids
Ingested and injected corticosteroids have been associated with SCD, which is illustrated by a case of a generalized cutaneous eruption several days after joint injection with triamcinolone acetonide.33 In another report, a patient developed an eruption in the body folds, later generalized, after topical application of a corticosteroid, first in ear drops and later in nasal spray.34 Traditional corticosteroid classification systems might be less reliable in predicting relevant allergens in corticosteroid SCD; comprehensive testing, including oral challenge, might be necessary to identify alternatives.33
Ethylenediamine
Ethylenediamine is an uncommon allergen in patch test populations. It is present in aminophylline35 and is utilized in the production of hydroxyzine36 and other piperazine-derived medications, such as cetirizine, levocetirizine, meclizine, and olanzapine. Several cases of SCD caused by aminophylline,35 cetirizine,36 and hydroxyzine37 have been reported, all in the setting of a positive patch test reaction to ethylenediamine.
When to Counsel About Systemic Exposures
In general, we usually do not counsel on systemic exposures to allergens at the final patch test reading unless the pattern of dermatitis or clinical history strongly suggests systemic exposure. In most cases, we find that counseling on topical allergen avoidance alone is sufficient to treat allergic contact dermatitis. Because of the restrictive nature of allergen-avoidance diets, counseling all patients on the potential for SCD might cause undue stress without much benefit. However, if a patient experiences persistent dermatitis on follow-up with topical avoidance alone, we often will delve into systemic exposures and counsel on further avoidance strategies, including medication and diet.
Final Interpretation
A multitude of chemicals have been reported as the source of SCD; these exposures can occur through ingestion, injection, and inhaled and cutaneous routes. Chemicals present in foods, medications, and beverages have been implicated. Systemic contact dermatitis is rare and should be considered when traditional avoidance of contact allergens is unsuccessful and the clinical pattern is consistent with SCD.