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.

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.

Many myths are given regarding the possible causes of baldness and its relationship with one's virility, intelligence, ethnicity, job, social class, wealth, etc. While skepticism may be warranted in many cases due to a lack of scientific validation, some claims may have a degree of underlying truth and are supported by research.

A 50% chance exists for a person to share the same X chromosome as his maternal grandfather. Because women have two X chromosomes, they have two copies of the androgen receptor gene, while men only have one. However, a person with a balding father also has a significantly greater chance of experiencing hair loss.

Because it increases testosterone levels, many Internet forums have put forward the idea that weight training and other forms of exercise increase hair loss in predisposed individuals. Although scientific studies do support a correlation between exercise and testosterone, no direct study has found a link between exercise and baldness. However, a few have found a relationship between a sedentary life and baldness, suggesting some exercise is beneficial. The type or quantity of exercise may influence hair loss.

Testosterone levels are not a good marker of baldness, and many studies actually show paradoxical low testosterone in balding persons, although research on the implications is limited.

Emotional stress has been shown to accelerate baldness in genetically susceptible individuals.

Stress due to sleep deprivation in military recruits lowered testosterone levels, but is not noted to have affected SHBG. Thus, stress due to sleep deprivation in fit males is unlikely to elevate DHT, which is one cause of male pattern baldness. Whether sleep deprivation can cause hair loss by some other mechanism is not clear.

Levels of free testosterone are strongly linked to libido and DHT levels, but unless free testosterone is virtually nonexistent, levels have not been shown to affect virility. Men with androgenic alopecia are more likely to have a higher baseline of free androgens. However, sexual activity is multifactoral, and androgenic profile is not the only determining factor in baldness. Additionally, because hair loss is progressive and free testosterone declines with age, a male's hairline may be more indicative of his past than his present disposition.

Many misconceptions exist about what can help prevent hair loss, one of these being that lack of sexual activity will automatically prevent hair loss. While a proven direct correlation exists between increased frequency of ejaculation and increased levels of DHT, as shown in a recent study by Harvard Medical School, the study suggests that ejaculation frequency may be a sign, rather than a cause, of higher DHT levels. Another study shows that although sexual arousal and masturbation-induced orgasm increase testosterone concentration around orgasm, they reduce testosterone concentration on average (especially before abstinence) and because about 5% of testosterone is converted to DHT, ejaculation does not elevate DHT levels.

The only published study to test correlation between ejaculation frequency and baldness was probably large enough to detect an association (1390 subjects) and found no correlation, although persons with only vertex androgenetic alopecia had had fewer female sexual partners than those of other androgenetic alopecia categories (such as frontal or both frontal and vertex). One study may not be enough, especially in baldness, where there is a complex with age. Marital status has been shown in some studies to influence hair loss in cross-sectional studies (NHANES1).

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.

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.

Androgenic alopecia is typically experienced as a "moderately stressful condition that diminishes body image satisfaction". However, although most men regard baldness as an unwanted and distressing experience, they usually are able to cope and retain integrity of personality.

Although baldness is not as common in women as in men, the psychological effects of hair loss tend to be much greater. Typically, the frontal hairline is preserved, but the density of hair is decreased on all areas of the scalp. Previously, it was believed to be caused by testosterone just as in male baldness, but most women who lose hair have normal testosterone levels.

Radiation induces hair loss through damage to hair follicle stem cell progenitors and alteration of keratin expression. Radiation therapy has been associated with increased mucin production in hair follicles.

Studies have suggested electromagnetic radiation as a therapeutic growth stimulant in alopecia.

It is commonly seen with certain hair styles or braiding patterns that pull the hairline forcefully towards the vertex of the scalp, and has been reported more often in African American women (as some wear their hair tightly pulled back), in whom it can cause scarring. It has also been seen in female ballerinas, and in cultural traditions where the hair is voluntarily not cut in religious obeisance, the latter caused by progressively increasing weight of the hair itself. Traction alopecia is mechanical in cause, rather than androgenic, and treatment is typically not pharmaceutical. Management includes cessation of the chronic traction, cosmeses, with surgical restoration reserved for more severe cases.

Traction alopecia is a substantial risk in hair weaves, which can be worn either to conceal hair loss, or purely for cosmetic purposes. The former involves creating a braid around the head below the existing hairline, to which an extended-wear hairpiece, or wig, is attached. Since the hair of the braid is still growing, it requires frequent maintenance, which involves the hairpiece being removed, the natural hair braided again, and the piece snugly reattached. The tight braiding and snug hairpiece cause tension on the hair that is already at risk for falling out. Traction Alopecia is one of the most common causes of hair loss in African American women.

Sikh men are also susceptible to traction alopecia if the hair under the turban is tied too tightly for many years.

Other causes include:

- Hairstyle. Although the aforementioned style is one of the culprits, hairstyles such as dreadlocks and single (extension) braids can also have the same effect. Men and women who have suffered from traction alopecia have found that the hair loss occurs most at the hair line—primarily around the temples and the sides of their heads.

- Headgear. Compressive safety helmets worn tightly and closely to the scalp are a cause of traction alopecia. The lining of tightly fitted safety helmets like those worn for activities such as motorcycling, cycling, skiing and snowboarding are responsible for the constant rubbing and tugging of localised areas of the hair and scalp. Frequent wearers or those who use such helmets for prolonged periods seem more likely to suffer traction alopecia.

- Chemicals. A condition known as CCCA (central cicatricial centrifugal alopecia), seen almost exclusively in African American women, can cause extensive hair loss. It is caused by a combination of too much stress (traction) on the hair and the use of harsh relaxers and dyes.

Many medications are being studied, including abatacept, MEXIS/M6S, triamcinolone, secukinumab, tralonkinumab, apremilast, botulinum toxin, INCB018424, bimatoprost, clobetasol, AS101, autologous platelet-rich plasma, topical minoxidil, and nitric oxide gel. Some of these medications are approved for other diseases, others are not available outside of studies.

In 2014, preliminary findings showing that oral ruxolitinib, a drug approved by the US Food and Drug Administration (FDA) for bone marrow disorder myelofibrosis, restored hair growth in three individuals with long-standing and severe disease. The medicine costs almost USD $10,000 a month.

This condition is self-limiting. Improvements in grooming techniques and in environmental conditions will correct the abnormality.

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.

Avoid aggressive brushing and grooming, strong chemicals, permanents, straightening, and similar hair-damaging habits.

The exact genetic mutation that causes congenital circumscribed, localized, and nevoid hypertrichosis is unknown.

There is no standard treatment for alopecia universalis. Many treatments have been explored, including immunomodulatory agents such as imiquimod. Tofacitinib citrate may also have benefits. In June 2014, it was reported that a 25 year old man with almost no hair on his body grew a full head of hair, and eyebrows, eyelashes, facial, armpit and other hair, following 8 months of treatment.

There is currently researching being done to find more treatments dependent on the different pre-existing conditions.

Studies are being conducted in which madarosis can be related to malignancy. A study by Groehler and Rose found that there was a statistical significance between these two. They concluded that patients malignancy lesions on the eyelid have a higher chance of having madarosis than a patient with a benign lesion. They stated that despite the fact that it is significant, the absence of madarosis does not mean the lesion cannot be malignant.

In many leprosy cases, madarosis is a symptom or a quality after diagnosis. However, in India, leprosy is common and researchers report a case of madarosis before diagnosis of leprosy with no skin lesions, only madarosis. This allowed for quicker treatment.

A main reason many people have madarosis is due to the chemotherapy drugs. There was a clinical trial in 2011 that tested an eyelash gel called bimatoprost. This gel enhanced the eyelashes in quantity and thickness. They tested this on 20 breast cancer patients who were undergoing chemotherapy. Results seemed positive, in that the group of people who used the gel had growth of eyelashes after the chemotherapy drugs.

CCCA tends to present itself in the 20s and progresses over 20–30 years. One should consider this diagnosis in African Americans with what appears to be a female-pattern hair loss.

Hair care products and shampoos can generally be used with any frequency desired, as long as the products are gentle and non-irritating to the scalp. Hair pieces, wigs, hats, and scarves may be used freely.

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.

Alopecia universalis can occur at any age, and is currently believed to be an autoimmune disorder, in which a person's immune system attacks the hair follicles. Genetic factors may contribute to AU as approximately 20% of those affected have a family member with alopecia.

Causes of noncicatricial alopecia include:

- Alopecia areata

- Anagen effluvium

- Androgenetic alopecia

- Dermatopathia pigmentosa reticularis

- Telogen effluvium

- Trichotillomania (Trichotillosis)

Hair diseases are disorders primarily associated with the follicles of the hair.

A few examples are

- Alopecia

- Bubble hair deformity

- Hair casts

- Hair loss

- hypertrichosis

- Ingrown hair

- Monilethrix

- Premature greying of hair

- Pattern hair loss

- Trichorrhexis invaginata

Many hair diseases can be associated with distinct underlying disorders.

Piedra are fungal diseases.

Hair disease may refer to excessive shedding or baldness (or both). Balding can be localised or diffuse, scarring or non-scarring. Increased hair can be due to hormonal factors (hirsutism) or non-hormonal (hypertrichosis). Scalp disorders may or may not be associated with hair loss.

Genetic forms of localized autosomal recessive hypotrichosis include:

There are various causes of madarosis.

- Ophthalmological conditions: blepharitis is an infection of the eyelid. Anterior blepharitis is either "staphylococcal blepharitis,"or "seborrhoeic blepharitis" and posterior blepharitis is due to the meibomian gland.

- Dermatologic conditions: there are multiple types of dermatological conditions that can result in madarosis. These include Atopic dermatitis, Seborrhoeic dermatitis atopic dermatitis, and Psoriasis on the eyelids can result in madarosis. Others include: frontal fibrosing alopecia, ulerythema ophryogenes, acne rosacea, telogen effluvium, follicular mucinosis, and cutaneous sarcoidosis.

- Nutritional defects: Severe malnutrition can cause chronic hair loss. Hypoproteinemia causes hair loss by early onset of telogen. Zinc deficiencies like acrodermatitis enteropathica, can lead to the loss of eyebrow/eyelash hair. Other deficiencies like biotin and iron make it possible for loss of hair as well.

- Infections: There are many bodily infections that can cause the loss of eyelashes/eyebrows. The most common infection may be leprosy, such as lepromatous leprosy. Syphilis or other viral infections like herpes or HIV can cause the loss of eye hair as well. Fungal infections, like paracoccidioidomycosis, trichophyton, or microsporum, are also possible infection causes.

- Trauma: Most trauma injuries cause madarosis from the psychological standpoint, known as trichotillomania

- Drugs/Medications: Crack cocaine or chemotherapy drugs. Other drugs include:propranolol, valproic acid, barbiturates, MMR vaccine, botulinum toxin, epinephrine, antithyroid drugs, anticoagulants, and lipid-lowering drugs

- Genetics

- Autoimmune disorders: alopecia areata, discoid lupus erythematosus, chronic cutaneous lupus erythmatosus, Graham-Little syndrome, and Parry Romberg syndrome

- Other diseases: hypothyroidism, hyperthyroidism, hypoparathyroidism, hypopituitarism, and amyloidosis

There only prevention method is determining the underlying condition before treatment options are too late.

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

Traction alopecia is a form of alopecia, or gradual hair loss, caused primarily by pulling force being applied to the hair. This commonly results from the sufferer frequently wearing their hair in a particularly tight ponytail, pigtails, or braids. It is also seen occasionally in long-haired people who use barrettes to keep hair out of their faces. Traction alopecia is recession of the hairline due to chronic traction, or hair pulling, and is characterized by a fringe along the marginal hairline on physical exam. Even though this "fringe sign" is considered a useful clinical marker of this condition, cases of frontal fibrosing alopecia presenting with an unusual retention of the hairline (pseudo-fringe sign) have been described.