Inflammation of the hair follicles or bacterial infection of the scalp can also cause itching.

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The process involves slathering on a carbon-based lotion, which absorbs the laser light and damages the hair follicles.

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New research suggests that hair diameter increases through a person's mid-30s, compensating for the gradual loss of active hair follicles.

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The ARTAS system itself is only used to extract the individual hair follicles under guidance of a doctor using computer imaging.

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"I apparently clogged a lot of the pores and some follicles, and choked them out during the six-week run, " he recalled.

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But it will cause dirt and oil to accumulate on your scalp and hair follicles, and could cause inflammation and irritation that might stunt hair growth.

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In FUE, individual follicles of hair are transplanted from an area on the scalp with lots of hair to the portions of the scalp where the hair is thinning.

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Common problems include overactive oil glands, bacteria growth within follicles and pores and problems with the keratinization process, where cells are normally sloughed off the skin, pushed out of the hair follicle and replaced by new cells.

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In both cases men (who are hairier than women, as measured by the density of follicles and the length of the vellus hair) were better off than women when the bugs were released on unshaven patches of skin, though there was no significant difference between the sexes when they were shaved.

ECONOMIST: Body hair