Scalp hair goes through three phases of growth. First is an active growth phase which lasts for two to six years, followed by a short two to three week transition phase, and finally an approximately three-month resting phase at the end of which the hair sheds. The average person sheds 100 hairs every day. However, some medical conditions can contribute to a faster than average hair loss and sudden thinning of the hair. If you experience sudden hair loss, consult your doctor.
Tinea Capitis
Also known as ringworm, this is a fungal infection of the scalp. The ringworm fungus grows best in humid conditions. Athletes who wear helmets and sweat are at higher risk. Minor injuries to the scalp can also increase the risk of infection. Tinea capitis typically causes patchy hair loss. The hair does not actually fall out, but rather breaks off at the surface of the scalp. The scalp will become itchy and flake or develop inflamed scaly areas. Oral antifungal medications are the treatment of choice for this condition.
Telogen Effluvium
Emotional or physical stress can induce large numbers of hair follicles to enter a resting phase all at the same time. Hair loss does not occur until weeks or months after the event. Telogen effluvium can affect up to three-quarters of your hair, producing an overall thinning on the scalp. The affected hairs will all shed at around the same time, appearing like handfuls of lost hair when you shampoo or brush. Hair might appear thinner in spots, but completely bald spots are rare. The condition typically resolves within six to eight months. Extreme emotional stress can cause telogen effluvium. Other causes include a prolonged illness, major surgery or a serious infection with high fever. Sudden changes in hormone levels, like that experienced with pregnancy and childbirth, are also causes of this type of hair loss.
Alopecia Areata
Alopecia areata is an autoimmune disease. The cause is unknown, although there are theories that a virus or some environmental factor might trigger the condition. Hair loss is typically in patches, if there is total loss of scalp hair the condition is called alopecia totalis. In alopecia, white blood cells attack the hair follicle, stopping hair growth and triggering hair loss. The hair usually grows back, although it might be lost again in the same area or in a new area. Treatments include UV light therapy, topical creams containing corticosteroids or steroid injections into the affected areas.
Medication
Sudden thinning of hair can be a side effect of certain medications. Chemotherapies to treat cancer are the most recognized medications that cause sudden hair loss. These medications kill fast-growing cells, including hair cells. Other medications that might cause hair loss include birth-control pills, the antidepressant lithium, heart medications called beta-blockers, the blood thinners warfarin and heparin, amphetamines and the Parkinson's medication levodopa. Hair that is lost as a side effect of medication typically returns once the medication is no longer required.
Other Causes
Thyroid disorders can cause sudden thinning of the hair. This includes hypothyroidism and hyperthyroidism. Nutritional deficiencies of protein, iron, zinc or biotin can cause hair to shed at a higher rate. Very restrictive diets or women with heavy menstrual flows can develop these deficiencies. If you have questions about whether your diet provides sufficient nutrients, consult your doctor or dietitian.
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