Research is looking into connections between hair loss and other health issues. While there has been speculation about a connection between early-onset male pattern hair loss and heart disease, a review of articles from 1954 to 1999 found no conclusive connection between baldness and coronary artery disease. The dermatologists who conducted the review suggested further study was needed.

Environmental factors are under review. A 2007 study indicated that smoking may be a factor associated with age-related hair loss among Asian men. The study controlled for age and family history, and found statistically significant positive associations between moderate or severe male pattern hairloss and smoking status.

Vertex baldness is associated with an increased risk of coronary heart disease (CHD) and the relationship depends upon the severity of baldness, while frontal baldness is not. Thus, vertex baldness might be a marker of CHD and is more closely associated with atherosclerosis than frontal baldness.

The condition affects 0.1%–0.2% of the population, and occurs equally in both males and females. Alopecia areata occurs in people who are otherwise healthy and have no other skin disorders. Initial presentation most commonly occurs in the late teenage years, early childhood, or young adulthood, but can happen at any ages. Patients also tend to have a slightly higher incidence of conditions related to the immune system, such as asthma, allergies, atopic dermatitis, and hypothyroidism.

Male pattern hair loss is believed to be due to a combination of genetics and the male hormone dihydrotestosterone. The cause in female pattern hair remains unclear.

Woolly hair nevus (alternatively spelled "Wooly hair nevus") is a congenital condition in which hair in a circumscribed area of the scalp is kinked or woolly.

Acquired hypertrichosis lanuginosa is commonly present with cancer. This condition is also linked to metabolic disorders, such as anorexia, hormone imbalances, such as hyperthyroidism, or as a side effect of certain drugs.

Acquired generalized hypertrichosis may be caused by cancer. The resulting hair growth is known as malignant down. The mechanism behind cancer induced hypertrichosis is unknown. Oral and topical minoxidil treatments are also known to cause acquired generalized hypertrichosis.

Oil production in the sebaceous glands increases during puberty, causing comedones and acne to be common in adolescents. Acne is also found premenstrually and in women with polycystic ovarian syndrome. Smoking may worsen acne.

Oxidation rather than poor hygiene or dirt causes blackheads to be black. Washing or scrubbing the skin too much could make it worse, by irritating the skin. Touching and picking at comedones might cause irritation and spread infection. It is not clear what effect shaving has on the development of comedones or acne.

Some, but not all, skin products might increase comedones by blocking pores, and greasy hair products (like pomades) can worsen acne. Skin products that claim to not clog pores may be labeled noncomedogenic or non-acnegenic. Make-up and skin products that are oil-free and water-based may be less likely to cause acne. It is not known whether dietary factors or sun exposure make comedones better, worse or have no effect.

A hair that does not emerge normally can also block the pore and cause a bulge or lead to infection (causing inflammation and pus).

Genes may play a role in the chances of developing acne. Comedones may be more common in some ethnic groups. People of recent African descent may experience more inflammation in comedones, more comedonal acne, and earlier onset of inflammation.

Congenital hypertrichosis lanuginosa may be caused by an paracentric inversion mutation of the q22 band of chromosome 8; however, it could also be possibly the result of a spontaneous genetic mutation rather than inheritance. This form is an autosomal dominant (not located on the sex chromosomes) cutaneous disorder, that affects the skin.

- Generalized hypertrichosis

Congenital generalized hypertrichosis has a dominant pattern of inheritance and has been linked to chromosome Xq24-27.1. An affected female (carrying the hypertrichosis gene) has a 50% chance of passing it to her offspring. An affected male will pass this form of hypertrichosis to his daughters, but never the sons.

- Generalized hypertrichosis terminalis

Congenital generalized hypertrichosis terminalis is thought to be caused by genetic changes on chromosome 17 resulting in the addition or removal of millions of nucleotides. The gene MAP2K6 may be a factor contributing to this condition. This condition may also be due to the change in the chromosome affecting the transcription of genes.

Other hypertrichosis patterns

Porphyria cutanea tarda may manifest in some patients as hypertrichosis on the face (mainly on top of the cheeks).

Risk factors for the development of acne, other than genetics, have not been conclusively identified. Possible secondary contributors include hormones, infections, diet and stress. Studies investigating the impact of smoking on the incidence and severity of acne have been inconclusive. Sunlight and cleanliness are not associated with acne.

In most cases which begin with a small number of patches of hair loss, hair grows back after a few months to a year. In cases with a greater number of patches, hair can either grow back or progress to alopecia areata totalis or, in rare cases, alopecia areata universalis.

There is no loss of body function, and effects of alopecial areata are mainly psychological (loss of self-image due to hair loss), although these can be severe. Loss of hair also means the scalp burns more easily in the sun. Patients may also have aberrant nail formation because keratin forms both hair and nails.

Hair may grow back and then fall out again later. This may not indicate a recurrence of the condition, but rather a natural cycle of growth-and-shedding from a relatively synchronised start; such a pattern will fade over time. Episodes of alopecia areata before puberty predispose to chronic recurrence of the condition.

Alopecia can be the cause of psychological stress. Because hair loss can lead to significant changes in appearance, individuals with it may experience social phobia, anxiety, and depression.

Hair follicle nevus (also known as a "Vellus hamartoma") is a cutaneous condition that presents as a small papule from which fine hairs protrude evenly from the surface.

Frontal Fibrosing Alopecia has been most often reported in post-menopausal women with higher levels of affluence and a negative smoking history. Autoimmune disease is found in 30% of patients.

The predisposition to acne for specific individuals is likely explained by a genetic component, a theory which is supported by studies examining the rates of acne among twins and first-degree relatives. Severe acne may be associated with XYY syndrome. Acne susceptibility is likely due to the influence of multiple genes, as the disease does not follow a classic (Mendelian) inheritance pattern. Multiple gene candidates have been proposed including certain variations in tumor necrosis factor-alpha (TNF-alpha), IL-1 alpha, and CYP1A1 genes, among others. Increased risk is associated with the 308 G/A single nucleotide polymorphism variation in the gene for TNF.

Worldwide, KP affects an estimated 30-50% of the adult population and approximately 50-80% of all adolescents. It is more common in women than in men, and is often present in otherwise healthy individuals. The skin condition is prevalent in persons of all ethnicities. No particular ethnicity is at higher risk for developing keratosis pilaris. Although keratosis pilaris may manifest in persons of any age, it usually appears within the first decade of life and is more common in young children. In most cases, the condition gradually improves before age 30, however it can persist longer.

The decision to observe or treat a nevus may depend on a number of factors, including cosmetic concerns, irritative symptoms (e.g., pruritus), ulceration, infection, and concern for potential malignancy.

Improvement or stabilization of the condition has been reported with topical and intralesional corticosteroids, antibiotics, hydroxychloroquine, topical and oral immunomodulators, tacrolimus, and most recently, 5-alpha-reductase inhibitors. In one study, the use of anti-androgens (finasteride or dutasteride) was associated with improvement in 47% and stabilization in 53% of patients

Certain hair shampoos and ointments visually thicken existing hair, without affecting the growth cycle. There have also been developments in the fashion industry with wig design. The fashion accessory has also been shown to be a source of psychological support for women undergoing chemotherapy, with cancer survivors in one study describing their wig as a "constant companion". Other studies in women have demonstrated a more mixed psychosocial impact of hairpiece use.

Specialized scalp tattoos can mimic the appearance of a short buzzed haircut.

Using non-oily cleansers and mild soap may not cause as much irritation to the skin as regular soap. Blackheads can be removed across an area with commercially available pore-cleansing strips or the more aggressive cyanoacrylate method used by dermatologists.

Squeezing blackheads and whiteheads can remove them, but it can also damage the skin. Doing so increases the risk of causing or transmitting infection and scarring, as well as potentially pushing any infection deeper into the skin. Comedo extractors are used with careful hygiene in beauty salons and by dermatologists, usually after using steam or warm water.

Complementary medicine options for acne in general have not been shown to be effective in trials. These include aloe vera, pyridoxine (vitamin B6), fruit-derived acids, kampo (Japanese herbal medicine), ayurvedic herbal treatments and acupuncture.

Some acne treatments target infection specifically, but there are treatments that are aimed at the formation of comedones as well. Others remove the dead layers of the skin and may help clear blocked pores.

Dermatologists can often extract open comedones with minimal skin trauma, but closed comedones are more difficult. Laser treatment for acne might reduce comedones, but dermabrasion and laser therapy have also been known to cause scarring.

Macrocomedones (1 mm or larger) can be removed by a dermatologist using surgical instruments or cauterized with a device that uses light. The acne drug isotretinoin can cause severe flare-ups of macrocomedones, so dermatologists recommend removal before starting the drug and during treatment.

Some research suggests that the common acne medications, retinoids and azelaic acid, are beneficial and do not cause increased pigmentation of the skin.

Medical knowledge and documentation of this disorder is poor, likely due to a combination of factors including recent discovery, low prevalence, and the more or less aesthetic nature of the effects of the skin disorder. Thus the pathophysiology of Becker's nevus remains unclear. While it is generally considered an acquired rather than congenital disorder, there exists at least one case report documenting what researchers claim is a congenital Becker's nevus with genetic association: a 16-month-old boy with a hyperpigmented lesion on his right shoulder whose father has a similar lesion on his right shoulder.

The most extensive study to date, a 1981 survey of nearly 20,000 French males aged 17 to 26, served to disprove many commonly held beliefs about the disorder. In the French study, 100 subjects were found to have Becker's nevi, revealing a prevalence of 0.52%. Nevi appeared in one half the subjects before the age of 10, and between ages 10 and 20 in the rest. In one quarter of cases sun exposure seems to have played a role, a number apparently lower than that expected by researchers. Also surprising to researchers was the low incidence (32%) of Becker's nevi above the nipples, for it had generally been believed that the upper chest and shoulder area was the predominant site of occurrence. Pigmentation was light brown in 75% of cases (note: subjects were Caucasian), and average size of the nevus was 125 cm² (19 in²).

The cause of the various cicatricial alopecias is poorly understood. However, all cicatricial alopecias involve inflammation directed at the upper part of the hair follicle where the stem cells and sebaceous gland (oil gland) are located. If the stem cells and sebaceous gland are destroyed, there is then no possibility for regeneration of the hair follicle, and permanent hair loss results.

Cicatricial alopecias are not contagious. In general, cicatricial alopecias are not associated with other illnesses, and usually occur in otherwise healthy men and women.

Cicatricial alopecias affect both men and women, most commonly adults, although all ages may be affected. Epidemiologic studies have not been performed to determine the incidence of cicatricial alopecias. In general, they are not common.

The majority of patients with cicatricial alopecia have no family history of a similar condition. The one exception is Central centrifugal cicatricial alopecia, which primarily affects women of African ancestry and may occur in several women in the same family. While it is possible to have more than one type of hair loss condition, non-scarring forms of hair loss do not turn into scarring forms of hair loss.

A 1991 report documented the cases of nine patients with both Becker's nevus and malignant melanoma. Of the nine melanomas, five were in the same body area as the Becker's nevus, with only one occurring within the nevus itself. As this was apparently the first documented co-occurrence of the two diseases, there is so far no evidence of higher malignancy rates in Becker's nevi versus normal skin. Nonetheless, as with any abnormal skin growth, the nevus should be monitored regularly and any sudden changes in appearance brought to the attention of one's doctor.

Ultraviolet light from the sun causes premature aging of the skin and skin damage that can lead to melanoma. Some scientists hypothesize that overexposure to UV, including excessive sunlight, may play a role in the formation of acquired moles. However, more research is needed to determine the complex interaction between genetic makeup and overall exposure to ultraviolet light. Some strong indications that this is so (but falling short of proof), are:

- The relative lack of moles on the buttocks of people with dysplastic nevi.

- Freckles (spots of melanin on the skin, and distinct from moles) are known to be influenced by sunlight.

Studies have found that sunburns and too much time in the sun can increase the risk factors for melanoma. This is "in addition to" those who have dysplastic nevi being at higher risk of this cancer (the uncertainty is in regard to acquiring "benign" moles). To prevent and reduce the risk of melanoma caused by UV radiation, the American Academy of Dermatology and the National Cancer Institute recommends staying out of the sun between 10 a.m. and 4 p.m. standard time (or whenever one's shadow is shorter than one's height). The National Cancer Institute also recommends wearing long sleeves and trousers, hats with a wide brim, sunscreens, and sunglasses that have UV-deflecting lenses.

Razor burn is a less serious condition caused by shaving, characterized by mild to moderate redness and irritation on the surface of the skin. Unlike PFB, it is usually transient and there is no infection involved.

There is also a condition called "folliculitis barbae". The difference between the two is the cause of the inflammation in the hair follicles. Folliculitis barbae is caused by viral or bacterial infections, where pseudofolliculitis is caused by irritation from shaving and ingrown hairs.

A related condition, pseudofolliculitis nuchae, occurs on the back of the neck, often along the posterior hairline, when curved hairs are cut short and allowed to grow back into the skin. Left untreated, this can develop into acne keloidalis nuchae, a condition where hard, dark keloid-like bumps form on the neck. Both occur frequently in black men in the military, where it is so common that services often have widely known protocols for management

Although follicles were previously thought gone in areas of complete baldness, they are more likely dormant, as recent studies have shown the scalp contains the stem cells from which the follicles arose. Research on these follicular stem cells may lead to successes in treating baldness through "hair multiplication" (HM), also known as "hair cloning".

Per a May 2015 review, no successful strategy to generate human hair follicles, for hair regrowth, from adult stem cells has yet been reported. However, in April 2016, scientists from Japan published results of their work in which they created human skin from induced pluripotent stem cells; implanted into laboratory mice, the cells generated skin with hair and glands.

The term nevus is included in the names of multiple dermatologic syndromes:

- Basal cell nevus syndrome

- Blue rubber bleb nevus syndrome

- Dysplastic nevus syndrome

- Epidermal nevus syndrome

- Linear nevus sebaceous syndrome

Large and especially giant congenital nevi are at higher risk for malignancy degeneration into melanoma. Because of the premalignant potential, it is an acceptable clinical practice to remove congenital nevi electively in all patients and relieve the nevocytic overload.