Likewise, gold has been reported to cause SCD, with one case attributed to gold in a homeopathic cardiac medication.7 Gold SCD also should be considered in the setting of ingested gold-containing alcoholic beverages and historically has been associated with intramuscular gold sodium thiomalate for the treatment of rheumatoid arthritis.8
Metal implants, including prosthetic joints, stents, and other devices, have been implicated in SCD. (More to come on this topic soon; yes, dear reader, that is a teaser!)
Fragrances
Balsam of Peru
Secreted by the tree Myroxylon balsamum var pereirae, balsam of Peru (BOP) contains several potential allergens, including cinnamon oils (eg, eugenol, vanillin, cinnamates), coniferin derivatives, and benzoic acid derivatives.9 Foods and beverages associated with BOP include citrus, pickled vegetables, chocolate, ice cream, chili, pizza, tomatoes, wine, beer, gin, vermouth, flavored tea, and soft drinks.10 Flavoring agents, spices (eg, cloves, curry, vanilla, cinnamon, allspice, ginger, anise), and condiments (eg, ketchup, barbeque sauce) are potential sources, as are cough medicines, lozenges, and flavored tobacco.
Salam and Fowler10 described BOP-allergic patients whose condition improved with dietary restriction of BOP. Avoidance of tomatoes, citrus, spices, and cola most commonly contributed to improvement.10 Scheman et al9 proposed BOP subgroups, including the eugenol, vanillin, cinnamate, benzoate, ferulic acid, and coniferin groups. Targeted patch testing can identify relevant subgroups, and patients can focus dietary restrictions by subgroup.
Plants
Systemic contact dermatitis has been reported in association with a number of plants and herbals, including chamomile in tea,11 goldenrod in a medicated extract,12Hosta plantaginea roots,13 and garlic extract for hyperlipidemia.14 Many more have been described.
Propolis
Also known as bee glue, propolis comprises a mixture of balsams, resins, waxes, essential oils, pollen, cinnamic alcohol, and vitamins. It can be found in many cosmetic products, foods, and chewing gum.15 Propolis has been reported to be the source of SCD from ingestion of propolis capsules, which have been used to promote immune stimulation,15 and propolis solution as a natural tonic.16
Propylene Glycol
Propylene glycol (PG) can be found in (believe it or not) foods and medications. In foods, it typically is used for its softening, humectant, and preservative properties.17 Common food sources of PG include sauces, desserts, snack foods, and salad dressings.
Many topical prescription medications, including corticosteroids and newer nonsteroidal anti-inflammatory topicals, might contain PG; providers must specifically request PG-free products for PG-allergic patients. A detailed PG-avoidance diet lists products to avoid and products that are PG free.18