Both men and women are prone to  stretch marks (striae, singular stria or striae distensae) on several parts of their bodies, including the belly, thighs, hips, breasts, upper arms, and lower back. Stretch marks are a form of scarring on the skin: the marks often start off with a reddish hue and as they progress, take an off-color appearance. Stretch marks are often the result of the rapid stretching of the skin dermis associated with rapid growth, weight changes, pregnancy (usually during the last trimester) or hormonal changes associated with puberty, bodybuilding, or hormone replacement therapy. Recent study identified several genetic variants in elastin gene (ELN) that are significantly associated with stretch marks.

Cellulite is a condition when skin on thighs, hips, buttocks, and abdomen appears lumpy because of excess of fat beneath the skin. It is most common in women than men and even thin people are prone to it.There are many causes of cellulite including excessive weight, total body fat, poor diet, fad dieting, lack of physical activity, dehydration, hormone changes, and genetic predisposition. A small study of 200 lean women with cellulite and 200 BMI-matched controls identified two variations in ACE and HIF1A genes that were significantly associated with appearance of cellulite. Many treatments for cellulite, include massages, cellulite creams, lasers, and injections. Most of these treatments can work only in combination with a healthy, active lifestyle.

Acne (acne vulgaris) is most common in teenagers and young adults. It may also occur in adult women and men signaling hormonal imbalances. There are up to 3 million cases a year in the US. Of those affected, moderate to severe problems occur in 20%. Acne happens when hair follicles become clogged with dead skin cells and oil from the skin. Symptoms range from un-inflamed blackheads to pus-filled pimples or large, red, and tender bumps. In addition to hormonal changes and stress, genetics also contributes to the likelihood of acne.

Balanced levels of hydration is absolutely fundamental for healthy skin. Aquaporin channels, a family of integral cell membrane proteins, play central role in keeping our skin hydrated by allowing the movement of water and glycerol across the cell membrane. The quality of aquaporin channels in human skin is strongly affected by aging, chronic sun exposure, and inflammation. The most abundant (and best studied) aquaporin in the skin is the AQP3 gene. It transports water, glycerol, and small solutes (urea) across the plasma membrane hence regulating skin hydration, skin barrier recovery, and wound healing. Another group of genes expressed in skin are called claudins. They are tight junction membrane proteins that form paracellular barriers and pores that determine tight junction permeability. Genetic variations in the AQP3 and CLDN1 genes can result in their diminished expression and reduced activity. This, in the epidermis, leads to impairments in skin intrinsic hydration capacity and skin dryness.

A balance between free radicals and intrinsic antioxidants is necessary for proper physiological functioning as well as to maintain youthful and healthy skin. Increased amounts of free radicals contribute to a dangerous chain of reactions that target tissues and organs in the body, including skin. This can  trigger many chronic and late-onset diseases while also leading to premature aging by damaging the skin’s proteins and lipids. To prevent such an occurrence, a master regulator gene, NRF2 (NF-E2-Related Factor 2), prompts the activation of SOD2/CAT(enzyme/protein) when it is triggered by oxidative stress and electrophiles. These enzymes convert free radicals into less harmful products. Genetic variations in NRF2, SOD2, and CAT can result in reduced antioxidant activities which then increases risk of damage to the skin’s lipids and proteins.

Skin inflammation is the result of a complex biological process where the cells in the skin have a hyperactive response to allergens or toxins and produce inflammatory hormones called cytokines and chemokines. There are two types of inflammation: acute and chronic. Acute inflammation is a signal to the skin to start the repair process after being exposed to triggering stimulus, such as germs or environmental toxins. It can last from 2-4 days (generally the amount of time required for wounds or infections to heal) to up to 6 weeks. Chronic inflammation goes beyond six weeks and it serves no purpose. It becomes destructive and can damage the skin. There are a number of stimuli that induce chronic inflammation: overexposure to UV rays, stress, toxins (e.g. pollution, smoking, trauma, alcohol, immune reactions, infections etc), pathogens, and foreign bodies (dirt and debris). Chronic inflammation plays an important role in overall skin sensitivity, and susceptibility to wound infection. It often goes hand in hand with skin diseases, such as eczema, rosacea, and psoriasis. Chronic inflammation can also be triggered by excess of free radicals. In addition, genetic variations in several pro-inflammatory and anti-inflammatory cytokines genes are associated with higher risks of chronic skin inflammation.