By:  Dr. Ed Schulhafer, MD, CMES

 There are many reasons to advocate simplicity in skin care product formulations.  One reason is that the more ingredients introduced, the lower the benefit of the effective ingredients.  Another reason is economical.  The fewer ingredients used, the more cost effectively the product can be produced.  A third goal of skin care is efficacy.  There are not truly so many effective and proven ingredients in skin care products that have proven placebo controlled trials supporting their use.  From an allergist's viewpoint, the simpler, the better.  Each and every ingredient carries the risk of causing contact allergy. 

 While most of us patch test to either 24 or 45 ingredients capable of causing contact allergy, even the 45 standardized tests from Dormer only identify about 50% of all causes of contact allergy.  When we need to test for other kinds of contestants, we either have to purchase less standardized materials for patch testing or devise our own standardized tests from raw materials.  There are no patch tests available for botanicals.  To just apply the source plant for the standard 48 to 72 hours in an inadequate amount of time for contact testing.  These no standardized tests must be kept on the skin for 6 to 7 days.  And the potency of the plant varies with where it was grown and even what conditions existed during the growing season.  It is  truly a wild goose chase.

 So what are common contact allergies from cosmetics?  The most common category is from preservatives.  Formaldehyde releasing products are a huge and common source for contact allergy.  This includes quaternion 15 in shampoos and conditioners, eye makeup, foundation, lotions and creams, shaving products, bath gels, soaps, and dusting powders.  Diazolidinyl urea and imidazolidinyl urea are two other commonly used preservatives that can cause sensitization.  Other common formaldehyde releasing products include bronopol and DMDM hydantoin.  Approximately 10% of all those tested are reactive to this class of preservative.

 A rare cause of cosmetic allergy is from parabens.  While 1.5% of the population is technically allergic to parabens, the reaction typically occurs only when the skin is stressed or broken from another condition such as eczema.  When contact allergy does occur it is difficult to find from patch testing as the standardized test is often too weak to solicit the reaction or it is not applied to the stressed area of skin. 

 PABA, para-aminobenzoic acid, used in sunscreens 15 years ago is rarely a cause of contact allergy today.  It has been largely eliminated as an ingredient.  More commonly, benzophenone is the contactant allergy in sun screens now. 

 Dermatitis limited to the upper eyelid is often from the acrylic used in nail polish or artificial nails. 

 Propylene glycol  is another common sensitizer used in cosmetics, detergents, shampoos, hair dressings, insect repellents and toothpastes.  It is a commonly encountered preservative.  Glycerin is a better vehicle to be used as a solvent because reactions to it are rare. 

 While beeswax rarely causes sensitization,  if it is cross contaminated with propolis (bee glue) sensitization is certainly possible.  Lanolin rarely causes reactions unless applied to stasis eczemas and ulcers.

 The next most common category of reactions to cosmetics after preservatives is fragrances.  Remember that the term fragrance free does not mean no fragrance.  This term can be applied to a product that uses masking fragrances to make a product odorless.  Balsum of Peru is the most common fragrance sensitizer.  Musk ambrette in shaving cream is a most common fragrance that causes contact dermatitis.

 Many bath preparations contain the sensitizer, cocamidoproyl betaine.  Eye make up preparations may be cross contaminated with nickel, the biggest sensitizer of them all.  It can be from the eyelash curling instrument or the mascara applicator.  Cobalt and chromate can be included as coloring agents and they can sensitize as well.  In the case of eyelid dermatitis one must consider gold, shampoo ingredients and the nail cosmetics already mentioned.

 Hair coloring agents can cause sensitization.  p-phenlenediamine (PPDA), toluene-2,5-diamine and p-aminophenol are all active sensitizers.  Ammonium persulfate used to lighten the color of hair can also cause allergic reactions.  Henna reactions are rare.  A newer sensitizer in hair coloring agents is glycerol monogycol thiamate.  This one used in permanents can persist for as long as it is present in the hair in contrast to PPDA that usually only causes reactions when it is first applied.

 Facial makeup can cause reactions due to the use of dyes such as D&C Red no. 36, no. 31, no. 19 and D&C yellow no. 10 and no. 11.  Artificial nails are formulated with many possible sensitizers such as the various methacrylic acid esters all referred to as monomers, demethcrylates or methacrylates.  These reactions occur around the nail bed and sometimes the upper eyelids and neck.