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 invaginataMany 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. See also
List of cutaneous conditions

References
External links

https://www.nlm.nih.gov/medlineplus/hairdiseasesandhairloss.html
Straining of the hamstring, also known as a pulled hamstring, is defined as an excessive stretch or tear of muscle fibers and related tissues. Hamstring injuries are common in athletes participating in many sports. Track and field athletes are particularly at risk, as hamstring injuries have been estimated to make up 29% of all injuries in sprinters. Hamstring injuries can also come with a hip injury from sprinting. Symptoms for a hip injury are pain, aching and discomfort while running or any physical exercise. The biceps femoris long head is at the most risk for injury, possibly due to its reduced moment of knee and hip flexion as compared to the medial hamstrings. Causes of hamstring strain
The muscle group is prone to injuries due to the explosive nature of movement in sports and thus causing overload and overstretching of the hamstring musculature. The other causes may be:

Previous injury
Poor muscle strength
Poor flexibility
Inadequate warm-up
Fatigue
Imbalance
OveruseThis condition is most commonly seen in:

Athletes involved in soccer, baseball, football, rugby
Dancers and water skiers
Sports involving cross-country skiing, downhill skiing, judo, cricket, and bull riding

Diagnosis
Grades
Grade 1
Sensation of cramp or tightness and a slight feeling of pain when the muscles are stretched or contracted. Grade 2
With a grade two hamstring strain there is immediate pain which is more severe than the pain of a grade one injury. It is confirmed by pain on stretch, swelling and contraction of the muscle. Grade 3
A grade three hamstring strain is a severe injury.