Q. My son has bad acne. What foods should he avoid? What's the best treatment? And what about tea tree oil?

A. Amazingly enough, acne is not worsened by chocolate, soft drinks, fried foods, shellfish or milk products. In a study, 65 acne patients who ate two concentrated chocolate bars a day for a month did not get worse.

A survey of 47,355 nurses found no association between severe teenage acne and eating pizza, sweets or french fries.

But if certain foods worsen your son's acne, then by all means avoid them.

Regarding tea tree oil, a systematic review of six electronic databases concluded that the data was promising but not compelling. And witch hazel bark, Vitex agnus-castus, bittersweet nightshade, brewer's yeast and Chinese duckweed don't seem to work.

For mild acne, I like topical retinoids — related chemically to vitamin A — like tretinoin, adapalene or tazarotene. If these don't work out, switch to something like nonprescription benzoyl peroxide cream or wash or prescription azelaic acid. The latter is a natural material produced by a yeast that lives on normal skin and kills acne-causing germs. The above topicals also help unplug acne pores. For dry or sensitive skin, keep benzoyl peroxide strength below 5 percent and avoid irritating vehicles such as hydroalcoholic gels and solutions.

Topical antibiotics like erythromycin and clindamycin also work but should not be used alone because of bacterial resistance. Salicylic acid is moderately effective. Azelaic acid, sulfur, resorcinol, sodium sulfacetamide, aluminum chloride and zinc don't work as well as the others.

Teens are notoriously bad at daily skin treatments, so tell us if they don't like their feel and prefer something different, like gels, foams, pads, medicated washcloths or washes. Warn teens that they take two to three months to start to work, and that acne often lasts more than five years. For back acne, one trick is to spray clindamycin foam on the shower wall and rub the back against the wall.

Antibiotics pills may be needed. Doxycycline and minocycline work better than tetracycline. Erythromycin works but often leads to resistant germs. Trimethoprim-sulfamethoxazole and trimethoprim alone also work in cases where other antibiotics can't be used. Doxycycline can cause easy sun burning. Minocycline can cause rare hepatitis, and also pigmentation of the skin (like the shins and in acne scars), mucous membranes, and teeth, especially with long-term use.

Accutane, or isotretinoin, is related to vitamin A and works for acne resistant to other treatments or which is causing physical or psychological scars. It can cause birth defects in pregnancy. Mood disorders, depression and suicides have been reported, but cause and effect has never been confirmed. In fact, treatment of severe acne with isotretinoin can reduce depression.

Dr. Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i John A. Burns School of Medicine. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.