Prolonged immersion removes more natural oils from her skin.
The flexibility and elasticity of your skin is conserved by water in the deeper layers of the skin. Natural oils, or lipids, are produced by your outer skin --- the stratum corneum --- to prevent that moisture from evaporating. Sustained immersion in water removes these lipids, causing evaporation, which shrinks the cells and causes them to crack and dry. Even a hot shower can remove important oils. Prolonged swimming can wreak havoc. The trick is to moisturize.
Humectant Moisturizers
Humectant moisturizers go to the source of the problem: the loss of oils in the stratum corneum. These substances are not oils per se, but compounds that penetrate into the stratum corneum. Humectants attract water and hold it in place. Glycerin, or glycerol, is a commonly sold humectant. It can also inhibit bacterial growth. Urea and glycolic acid are also humectants that are found in some skin moisturizers. Athletes can apply humectant products after they swim.
Occlusive Moisturizers
Occlusive moisturizers cover the skin to occlude, or block, evaporation loss. Unlike humectants, these do not attract or hold water, but they do prevent evaporation until the body can transport more water into the stratum corneum. Occlusive moisturizers are blended with water in different ratios to produce creams, ointments or lotions. Sunblocks are frequently used by swimmers before workouts, and many sunblock products advertise the use of occlusive moisturizers such as coconut oil, mineral oil and even sheep's wool oil, called lanolin. If re-applied frequently during immersion, occlusive moisturizers can help prevent dry skin. Caution is advised for lanolin products because some people are allergic to it.
Antimicrobials
One of the hazards of swimming, especially prolonged swimming that strips the skin of protective oils, is that bacteria in the water can exploit the erosion of oils to penetrate into small lesions to produce infections and rashes. A common pathogen in water, especially warm water, is pseudomonas aeruginosa. Skin ointments containing bacitracin are effective against pseudomonas aeruginosa, and these products contain occlusive moisturizers as well. These products should be applied locally in conjunction with other moisturizers. Scrubbing first with an antimicrobial soap, then moisturizing, might be a good strategy if a swimmer suspects she has been exposed.
Keratolytics
Chronic dry skin in swimmers can lead to a condition called ichthyosis, or scaly skin. This is caused by a buildup of dead epidermal tissue, consisting of a material called keratin. Keratolytics are substances that break down keratin so it can be emulsified and removed from the skin. Humectants in high concentration act as keratolytics. Products that advertise humectants ingredients may not have a sufficient concentration of the active ingredient to act as a keratolytic, so ensure that the product says it removes "dead skin" or ask your physician.
Tags: stratum corneum, from skin, into stratum, into stratum corneum, occlusive moisturizers