Hair loss (alopecia) can affect just your scalp or your entire body. It can be the result of heredity, certain medications or an underlying medical condition. Anyone — men, women and children — can experience hair loss.
Baldness typically refers to excessive hair loss from your scalp. Some people prefer to let their baldness run its course untreated and unhidden. Others may cover it up with hairstyles, makeup, hats or scarves. And still others choose one of the medications or surgical procedures that are available to treat hair loss.
Before pursuing any treatment option, talk with your doctor about the cause of and best possible treatments for your particular type of hair loss.

Hairy cell leukemia is a rare, slow-growing cancer of the blood in which your bone marrow makes too many B cells (lymphocytes), a type of white blood cell that fights infection. These excess B cells are abnormal and look "hairy" under a microscope. As the number of leukemia cells increases, fewer healthy white blood cells, red blood cells and platelets are produced.
Hairy cell leukemia affects more men than women, and it occurs most commonly in middle-aged or older adults.
Doctors aren't sure what causes hairy cell leukemia, and there is no cure. Hairy cell leukemia is considered a chronic disease because it may never completely disappear, although treatment can lead to a remission for years.

A hamstring injury occurs when you strain or pull one of your hamstring muscles — the group of three muscles that run along the back of your thigh.
You may be more likely to get a hamstring injury if you play soccer, basketball, football, tennis or a similar sport that involves sprinting with sudden stops and starts. Hamstring injury can occur in runners and in dancers as well.
Self-care measures such as rest, ice and over-the-counter pain medications are often all you need to relieve the pain and swelling associated with a hamstring injury. Rarely, surgery may be needed to repair a torn muscle.

Numbness in one or both hands describes a loss of sensation or feeling in your hand or fingers. Often, numbness in hands may be accompanied by other changes, such as a pins-and-needles sensation, burning or tingling. The arm, hand or fingers may feel clumsy or weak.
Numbness can occur along a single nerve, or it may occur in both hands in a symmetrical pattern.

Hay fever, also called allergic rhinitis, causes cold-like signs and symptoms, such as a runny nose, itchy eyes, congestion, sneezing and sinus pressure. But unlike a cold, hay fever isn't caused by a virus. Hay fever is caused by an allergic response to outdoor or indoor allergens, such as pollen, dust mites or pet dander.
Hay fever can make you miserable and affect your performance at work or school and interfere with leisure activities. But you don't have to put up with annoying symptoms. Learning how to avoid triggers and finding the right treatment can make a big difference.

Head lice are a very common problem, affecting millions of people each year — especially preschool and elementary school-aged children and their close contacts. Head lice are tiny, wingless, parasitic insects that live and feed on blood from your scalp.
Getting head lice isn't a sign of bad personal hygiene or an unclean living environment. This itchy infestation, also called pediculosis capitis, most commonly spreads through close personal contact and by sharing personal belongings.
Both over-the-counter and prescription medications are available to treat head lice. Following the directions properly and taking necessary steps at home are important to prevent head lice from recurring.

A heart attack usually occurs when a blood clot blocks the flow of blood through a coronary artery — a blood vessel that feeds blood to a part of the heart muscle. The interrupted blood flow that occurs during a heart attack can damage or destroy a part of the heart muscle.
A heart attack, also called a myocardial infarction, can be fatal. Treatment for heart attack has improved dramatically over the years. It is crucial to promptly recognize symptoms and call 911 or emergency medical help if you think you might be having a heart attack.