SKIN REACTIONS TO COSMETIC PREPARATIONS 19 In newer methods silicates in organic solvents or synthetic resins are used, e.g. formaldehyde with cresol and naphthalene in sulphuric acids forming condensation produces with keratin. The risks include physical damage from curling and pressing, with hair loss, thinning from excessive thioglycolate treatment, dermatitis from alkalis, resins, gums, formaldehyde and solvents. LIGHT SENSITIVITY AND PIGMENTATION In a skin capable of producing melanin, exposure to sunlight is followed by pigmentation. In those skins which do not pigment readily, i.e. the red haired and the Venetian blondes, the pigmentation is patchy, e.g. freckled. The darker the skin and hair, the more easily pigment is formed. Light sensitizing substances increase the sensitivity of the skin to ultra violet radiation. Sunburn follows minimal exposure with reddening, oedema or vesiculation of the affected parts followed by scaling, and deposition of pigment. Long excessive exposure leads to drying, atrophy, hyperkeratosis and skin cancer exactly as does exposure to radioactive sources. Actinic radiation produces changes in the collagen of the exposed areas as well as in the epidermis. The changes are similar to those associated with ageing and due to degeneration of the collagen, thinning and loss of elasticity, the skin becoming thin and transparent. Melanin, the skin pigment, protects against ultra violet radiation. The exposed areas in solar radiation are usually the forehead, cheeks, nose and ears, the back, sides and "v" of the neck and lower lip. The shoulders, outer arms, forearms, backs o[ the hands, and the scalp, if bald, are also affected as are the shins and feet in women. The upper lids, the upper lip, the area under the chin, the inner arms, the fingers, and the covered parts are relatively spared. U.V.R. may aggravate an already acute dermatitis. Light sensitizing substances may be applied locally or taken internal!y. From the cosmetic point of view the following are important: Eosin dyes, coal tar and its extracts, Psoralens (essential furocoumarin plant oils) often found in citrus oils (Bergamot, lime oil), mineral oils, dihydroxyacetone (used for colouring vitiligo and for suntan). Many drugs in common use for local application can cause light sensitiza- tion, in particular the sulphonamide% promethazine (phenergan), and the flame dyes (antiseptics). By mouth, chloropromazine (largactil) tetra- cyclines, phenergan and occasionally benadryl and other antihistamines. The sulphonamides including the chlorthiazides (diuretic and antidiabetic drugs) are given by injection. Vitamin B deficiency (nicotinic acid) also causes light sensitivity pigmentation and dermatitis (Pellagra).

20 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS In light sensitivity, a distinction is made between photo-toxic and photo- allergic agents similar to that between primary irritants and sensitizers. Photo-toxic reactions produce a non-allergic reaction and appear con- stantly if enough of the drug and suitable radiation are given. Photo-allergic reactions occur only in certain individuals as a result of the formation of a sensitizing decomposition compound within the skin by U.V.R. on the agent. Reactions can be reproduced by exhibition of the appropriate compound without light. Recently, photo-allergic reactions have been noted with blankophores (optical brightening agents) which are added to soaps, detergents, textiles, paper, etc. pAminobenzoic acid and paminosalicylic acid are also light sensitizers. Monoglyceryl paminobenzoic acid has been used as a sunscreen agent, and as such has been observed to produce sensitivity to light. pPhenylene diamine dermatitis is aggravated by exposure to light. In 1961, an extensive series of light sensitivity eruptions were seen following the use of soaps containing tetrachlorosalicylanilide (25). This is a good example of meddlesome additions of inadequately tested compounds to "harmless" toilet preparations. The compound, an excellent deodorant (bactericide) was added to soaps with an established sale. With the spring sunshine came a crop of red, scaling faces, the hands being less involved. The eyelids were often intensely swollen. After the acute stage, pigmenta- tion and lichenification remained. Patch tests were positive to •-1% of tetrachlorosalicylanfiide, and were aggravated by exposure to U.V.R. The action is similar to that of chloroxylenol, hexachlorophene and the quatern- ary ammonium compounds. The eruption subsided quickly when use of the soap was discontinued, but the light sensitivity persisted. The other halo- genated salicylanilides are also light sensitizers. Pigmentation is thus produced: (1) By exposure to sun, U.V.R. or Grenz ray, aggravated by light sensitizers. (2) By local irritation, e.g. the pigmentation of the shins due to long con- tinued toasting in front of fires (heat and actinic radiation). Pressure or friction pigmentation from tight clothing, massage and scratching vaga- bonds are traditionally pigmented. Irdtammation due to bacterial infection is followed by pigmentation. (3) Endogenous. Pregnancy, liver damage, excessive oestrogen, abnormal metabolism, e.g. Addisohs disease, Bronze diabetes (Haemochromatosis), porphyria, Vitamin B deficiency, starvation, and excessive vitamin A intake. (4) Chemical pigmentation. Argyria, a greyish blue pigmentation of the light-exposed areas due to