CLINICAL ASPECTS OF DRY SKIN 373 of skin has been a problem associated with soldiers xvho return from the tropics to California (19). According to temperature, humidity, and air motion thermoequivalent charts published by air conditioning engineers (20), relative humidities be- low 70 per cent at room temperature have no appreciable effect on human comfort related to subjective warmth or cold, but such studies do not relate to dry skin production and associated symptoms. Winter weather air conditioning systems should provide adequate moisture to the air. Ideally, the low relative humidity of summertime refrigerated air conditioning should be raised, but engineering problems and expense apparently prevent this. Air conditioning systems, winter and summer, should be built according to published specifications in order to prevent a feeling of draft. In many in- stances, this is often not the ease, (e.g. as in automobiles and window units). Patients with a proneness to dry skin should decrease their exposure to soaps, detergents, and lipid solvents. Hot •vater exposures are more harmful than cold water ones. A single long exposure seems to be less damaging than multiple short exposures. Protective gloves •vith s•veat absorbing liners, fre- quently changed, are useful. Mechanical irritation from clothing (especially •vool), household activities, and iob-related duties should be decreased and, of course, the patient should be encouraged to inhibit self-inflicted damage from rubbing and scratching. Topical Preparations: The pharmaceutical and cosmetic industries and extemporaneous prescription writing physicians have produced hundreds of products for topical use to prevent and treat dry skin. Plainly, this indicates that we do not as yet have the ideal preparation. Many of the popularly used water-dispersible bath oils and oil-in-water emulsion lotions and ereams give relief by coating the surface with a film that makes the skin look and feel more normal. They are easy to apply and are cosmetically acceptable. Their major mode of action probably relates to providing more cohesion for the unattached edges of squames and leaving an oily surface •vith a lower eoef[ieient of friction, but some products contain suf[ieient amounts of materials with a significant water vapor loss resistance to trap some moisture within the stratum eorneum. Their effectiveness is usually of short duration and, frequently, many applications per day are required. Other types of products are capable of absorbing •vater and temporarily holding this additional moisture on the skin surface. For generations, mothers have taught daughters about the beneficial el:Feet of mixtures of glycerin and rose water on dry hands, and, for many years, some dermatologists have prescribed mixtures of glycerin, peppermint •vater, and ethanol (9J). Mate- rials in the stratum eorneum, referred to as the natural moisturizing fac- tor (9,9,) have a combined hydroscopic ability that closely resembles that of glycerin (9,3). Propylene glycol and certain earbowax mixtures have similar

374 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS water absorbing powers, and Goldsmith and Baden (24) have used this power to treat ichthyosis. Unfortunately, the effectiveness of this group of products on dry skin is of short duration. More prolonged relief of dry skin signs and symptoms can be obtained by applying materials with a high water vapor loss resistance that prevent water from sweat and transepidermal transport from leaving the surface. Cert,ain water-in-oil emulsions and lipid materials of high viscosity provide this pro- tection. For example, petrolatuln has a water vapor loss resistance 17 times that of liquid paraffin and 170 times that of olive oil (25). But the cosmetic industry realizes the difficulty of promoting materials resembling petrolatum because of the cosmetic unacceptability related to a greasy feeling, sticki- ness, and interference with surface skin cooling. Their use is frequently limited to the more severe cases of dry skin. Sodium chloride, in various bases, and even set bathing, have been advo- cated for treatment of ichthyosis, but I know of no controlled study that shows a beneficial effect in ordinary dry skin problems. Urea has been advocated for various skin problems, and, in 1957 Klig- man (26) reviewed its usefulness in dermatologie therapy. Urea causes an increase of water uptake by stratum eorneum (27) has an antipruritie effect (28) increases percutaneous absorption (29) and clinical effetiveness (30) of hydrocortisone and has been shown to be useful in chronic eezemas (31) and various types of dryskin diseases (32). Some studies indicate its usefulness for ichthyosis (27, 33, 34), and uncontrolled studies suggest its benefit for dry skin (35, 37). But I know of no published double blind study showing that creams that contain urea are superior to ereams without it, although such studies are in progress. One double blind study on dry skin concluded that no statistical differences existed between creams that con- tain urea and aqueous creams (38). Topical and systemic pharmaceutical preparations are sometimes re- quired to treat severe dry skin and associated complications, but details of their indications are not germaine to this presentation. ADvv•usv. REACTIONS FI•OM Du¾ Srx• PuoDvcTs It has been observed that adverse reactions sometimes occur when prepara- tions are used on dry skin. Unfortunately, some manufacturers ignore this problem, when they state in their promotional literature, that no contrain- dications, precautions, or adverse reactions exist in their products. Allergic contact dermatitis may result from preservatives, perfumes, ex- cipients, solubilizers, emulsifiers, lubricants, and other constituents. Sympto- matic primary irritant type contact dermatitis has been observed (39). Non- specific discomforts include a warmth sensation, greasy or slimy feeling, and problems with contamination of clothing and papers. Disturbances in ecology