Q: Over the past three months, my hair seems to be thinning more on one side. Is it common in male pattern hair loss for it to be more on one side? I had a lot of stress about three months ago and have heard that this could be the cause. Is this possible? Should I use Rogaine to treat it? — B.R., Landover, MD

A: Regardless of the cause, hair loss is usually not perfectly symmetric. This applies to male pattern hair loss as well.

In your case, it is important to distinguish between telogen effluvium (shedding that can be due to stress) and hereditary or common baldness. The three month interval from the stressful period to the onset of hair loss is characteristic telogen effluvium, but you may have androgenetic alopecia as an underlying problem.

The two conditions are differentiated by identifying club hairs in telogen effluvium and miniaturized hair in androgenetic alopecia. In addition, a hair pull will be positive in telogen effluvium (when a clump of hair is grasped with the fingers, more than five hairs pull out of the scalp at one time) and will be negative in common baldness. The hair loss diagnosis can be made by a dermatologist.

Hair cuts do not affect either condition.

Rogaine (Minoxidil) is only effective in androgenetic hair loss and only marginally so. Finasteride is the preferred treatment if your hair loss is genetic when it is early and a hair transplant may be indicated if the hair loss progresses.

Shedding from telogen effluvium is reversible and does not require specific treatment.