Dermatological Services ↑

Patch Testing

Patch testing is a way of identifying whether a substance that comes in contact with the skin is causing a rash. At the Adult and Pediatric Dermatology we perform patch tests when an allergy is suspected or in cases when rash doesn’t improve or recurs with therapy.

We perform comprehensive testing using standard allergens present in North America. Consultation to determine the likely allergen involved is required before patch testing. Patch tests are placed usually on the back and reading is performed at 48 and 72 to 96 hours later. Our comprehensive panel of allergens includes the following: Benzocaine, Mercaptobenzothiazole (MBT), Colophony4-Phenylenediamine base, Imidazolidinyl urea Germall 115), Cinnamic aldehyde (Cinnamyl), Amerchol,
Carba mix, Neomycin sulfate, Thiuram mix, Disperse Red 17, Ethylenediamine dihydrochloride, Epoxy resin, Quaternium 15 (Dowicil 200), 4-tert-Butylphenolformaldehyde resin, Mercapto mix, Black rubber mix, Potassium dichromate Balsam Peru,
Nickelsulfate hexahydrate, Diazolidinylurea (Germall II,) di Alpha Tocopherol Acetate, Bacitracin, Mixed dialkyl thiourea, Disperse Orange 3, Paraben Mix Euxyl K 400, Fragrance mix, Glutaraldehyde2-Bromo-2-nitropropane-l3-diol (Bronopol), Sesquiterpene lactone mix, Thimerosal (Merthiolate), Dodecyl mercaptan4-Chloro-3,5-xylenol (PCMX), Ethyleneurea, melamine formaldehyde mix2-tert -Butyl-4-methoxyphenol (BHA), Goldsodiumthiosulfate, Ethyl acrylate, Glyceryl monothioglycolate (GMTG), Toluenesulfonamide formaldehyde resin, Methyl methacrylate, Cobalt(II) chloride hexahydrate, Tixocortol-21-pivalate, Budesonide Coconut diethanolamide, Triethanolamine, Cetyl stearyl alcohol (Lanette O), Tea Tree Oi,l Disperse Blue, Disperse Yellow, 34-Aminoazobenzene, Isoeugenol, Eugenol DMDM Hydantoin, Ylang-Ylang oil, Isopropyl myristate, Triclosan (Irgasan DP300) N,N-Diphenylguanidine, Polyoxyethylenesorbitanmonooleate(Tween 80), Dibutyl thiourea2-n-Octyl-4-isothiazolin-3-one, Disperse Blue, Compositae Mix, Lidocaine Copper sulfate, Mercuric chloride, Benzoylperoxide, Isoamyl-p-methoxycinnamate Lyral Octyl Salicylate, Benzalkonium chloride, Amidoamine Cocamidopropylbetaine Formaldehyde, Cl+Me-isothiazolinone (Kathon CG,100 ppm), Propylene glycol, Dimethyl dihydroxyethyleneurea (Fix.NF)

Common allergens tested

• Balsam of Peru: an aromatic mixture made from resins and essential oils. It is found in the haemorrhoid preparation Anusol, some perfumes and certain spices.
• Caine mix: local anaesthetics found in preparations for sore throats, sunburn remedies, haemorrhoid preparations, Wasp-eze. Used by dentists and doctors for minor surgical procedures.
• Carba mix: rubber 'accelerators' (chemicals used to speed up the polymerisation process in the manufacture of rubber). It is found in rubber gloves, shoes, bandages and elastic. Of those allergice to carba, 85 per cent are also allergic to thiuram.
• Chlorocresol: a substituted phenol preservative that kills bacteria. It is widely used in medications and some cosmetics. It cross-reacts with Dettol, which you should also avoid if you have a chlorocresol allergy.
• Chromate: a metal used for plating other metals to prevent rusting and in the manufacture of stainless steel. It is also found in cement and tanned leather.
• Cobalt: found in jewellery, dental implants, artificial joints, jet engines. Most patients are also allergic to nickel, and some are also allergic to chromate.
• Colophony: present in adhesives, plasters, paper, printing inks, medicated creams, glue tackifiers (stamps, labels), and cosmetics.
• Epoxy resin: plastics, used mainly as adhesives in the industrial setting but also by DIY enthusiasts. Found in two-component glues, such as Araldite.
• Formaldehyde: preservative frequently used in household products and in industry. Often found in cosmetics and shampoo.
• Fragrance mix: used in patch testing, this collection of eight individual fragrances detects about 75 per cent of patients allergic to perfume. If you have perfume allergy, you will not be allergic to all fragrances, but you cannot tell from the label which fragranced cosmetics are safe. Avoid all cosmetics listing 'parfum' as an ingredient on the label. Also found in air fresheners, washing powders and candles.
• Lanolin: produced by sheep to protect the fleece from the results of weathering. It is widely used in cosmetics, medical creams and bandages.