As a trichologist (specialist in hair and scalp health), I get asked a lot of questions about every hair problem under the sun. One thing I’ve noticed is that some questions recur again and again – so I thought I’d share some of the most common ones, as I know there will be plenty of readers who will want to know the answers to these frequently asked questions.

Q. I always suffer hair loss about three months after going on a crash diet. Why is that?

A. Going on a crash diet or just changing your diet drastically is a shock to the body. The hair registers this shock and a lot of growing hairs on the scalp pass prematurely to the ‘resting’ phase of the growth cycle, where they stay for about three months before the hair is released from the follicle and falls out. This explains why diffuse hair loss occurs about three months after the triggering cause or shock. With this type of hair loss, the hair recovers without any therapy as it cycles through its growth, rest and renewal phases, and lost hair is replaced by new hair.

Q. From the hair loss point of view, is it better to shampoo once a week or every day?

A. Whether you shampoo every day or once a week, the total amount of hair lost will be exactly the same. Hair falls out after spending three months in the resting phase, and the timing of the phases isn’t affected by washing frequency. Normally we lose about 70 hairs a day, which are replaced by new hairs.

Q. Is hair loss caused by hair follicles getting blocked up?

A. No, blocked hair follicles are not the cause of hair loss. However, follicles can get inflamed (folliculitis) and infected, and if severe infection is left untreated, that can lead to hair loss, and although rare, if severe also scarring.  

Q. Can hair turn white or gray as a result of stress?

A. The stem cells that produce melanocytes (that produce pigment) for the hair are located in an area termed the hair bulge, which is about midway up the hair follicle. One effect of stress is on the sympathetic nerves; with stress, these nerves increase their production of noradrenaline (norepinephrine), which makes your heartbeat and breathing faster. Interestingly, a recent study of the effects of stress in mice showed that the sympathetic nerves act directly on the melanocyte stem cells; these cells were quickly depleted and no pigment could then be generated. We think the same thing happens in humans – so yes, a pigmented hair can be replaced by a white hair as a result of stress.

Q. I don’t suffer hair loss but my hair never grows beyond my shoulders. Why is that?

A. The growth phase of the hair cycle for scalp hair differs considerably from one person to another, from around two years to 10 years. For those with a two-year growth cycle, hair will grow to a length of about 24 cm (shoulder length) before shedding, and 120 cm for those with a growth phase of 10 years.

Q. Is dry hair caused by a lack of moisture?

A. No, dry hair is a result of either damage to the hair from external influences such as chemical treatments, sun damage and overheating from blow dryers/straighteners, or a lack of sebum (natural oils) coating the hair. Moisture in the hair is also affected by relative atmospheric humidity, so it fluctuates depending on where you are located and your environment.

Q. Is hair dead?

A. Cells of the hair bulb divide rapidly so hair is very much alive in that area. However, by the time hair emerges from the skin, the cells have lost their nucleus so are no longer dynamic. From that point of view, the hair above the skin is dead.

Q. Does hair continue to grow after you die?

A. Hair does not continue to grow after you die. However, after death the skin loses its moisture and shrinks, exposing more hair and giving the impression that the hair has grown.

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