The warm weather is here and we finally feel more alive and active. People have reported that in summer, they feel like their hair is thicker and grows faster. Is it true that hair grows more in summer or is it just our imagination?
Hair growth is divided into three cycles: anagen, catagen and telogen. Anagen is the phase of active growth and lasts two to six years. Catagen is the transitional phase of two to three weeks where the hair follicle stops growing and shrinks. Telogen is the period when the hair sheds and falls out lasting approximately 100 days. Hair on our head usually is anagen 80-90 percent of the time and in telogen the other 10-20 percent. We typically lose 25 to 100 hairs a day. Overall, hair growth has been found to be affected by seasonal conditions as well as hormones and neurotransmitters in the body.
A Chilean study measured hair growth using trichograms of the hair from over 50 normal scalps over the course of ten years. A trichogram looks at hair under a microscope to determine what stage of growth the hair is in. The researchers found that the maximum amount of shedding of hair (telogen) occurred in October and the least was in June. This would indicate that hair growth is at its fullest in the spring to beginning of summer then shedding occurs throughout the summer and peak shedding is in the fall.
A small study performed in the U.K. monitored the growth of hair of 14 men for 18 months found that 90 percent of hair follicles on the scalp reached their peak of growth in March and this growth rate steadily dropped until September. Beard hair growth however, did peak in its growth from March to July to approximately 60 percent more than in winter. They did not find any seasonal differences in fingernail or toenail growth. Based on this study, scalp hair growth is also at its highest in the spring then gradually decreases throughout the summer.
Another study in Switzerland tested hair shedding of over 800 women over six years who had complained of excessive hair shedding.