A visit to Philip Kingsley can be hair-raising. Not to mention hair-brightening, hair-strengthening and even hair-thickening. One of the leading proponents of trichology (the study of hair and its diseases) in this country and England, Kingsley, 51, has made a science—and a success—out of treating such dread conditions as dandruff, split ends and itchy scalp. Among the 10,000 clients who swear by his hair care are such international head turners as Mick Jagger, Audrey Hepburn and even members of the British royal family. The Philip Kingsley Trichological Centre in New York and his clinic in London grossed $1.5 million last year, including the sale of more than 75,000 bottles of his own shampoos, conditioners and lotions.

Kingsley leaves the cutting, setting and styling of hair to beauticians. First-time customers at his salon on Manhattan's East Side have a personal consultation ($40) in the trichologist's spare but functional office. Clients are quizzed about their reasons for coming and their hair history (perms, coloring and fallout). Their hair is then scrutinized under an illuminated magnifying glass and analyzed in his lab to determine its structure and the extent of damage. Treatments ($27.50) may consist of a hair-and-scalp massage or a 10-minute session under infrared lamps, which help conditioners penetrate the hair follicles; these are usually repeated weekly for up to six weeks, then twice a month. Eventually a routine of quarterly visits in combination with home use of three Kingsley products (shampoo, conditioner and lotion at $6.95 each) is recommended to maintain healthy hair.

"There's no such thing as normal hair," proclaims Kingsley, and no single product can solve anyone's hair woes. Shampoo, for instance, "should be expected to gently cleanse the hair, that's all." He advises consumers to ignore claims about egg additives and categories like dry and oily and to "look for the shampoo with the fewest ingredients." Kingsley encourages people to "shampoo as often as you shower" and, for those with longer hair, to apply conditioner to the ends to prevent splitting.

The single most common problem Kingsley encounters is dandruff, a condition usually marked by a scaly but greasy scalp. It can be treated, he says, with a combination of a mild shampoo and an antidandruff scalp lotion—diluted mouthwash will do.

Kingsley believes "people should be better educated about their hair." To that end, he wrote The Complete Hair Book in 1979 (the paperback edition is to be published by Grove Press this month), which covers everything from cradle cap (a crusty scalp condition that afflicts infants) to hair weaving.

The son of a tailor, Kingsley grew up in the East End of London, where his boyhood dream was to become a doctor. But tight finances forced him to quit school at 15 and go to work in an uncle's barbershop for about $1 a week. At 17, he got a job with Ben Jones, one of London's top barbers, who eventually financed part of Kings-ley's three-year course at London's respected Institute of Trichologists. "I worked like a maniac," says Kingsley, who recalls taking his books with him on his honeymoon when, at age 20, he married his first wife, Betty (they divorced in 1977).

It was at Jones' shop that Kingsley cultivated celebrity clients like Laurence Olivier. They followed him when he moved on to Riché, a ladies' salon where he cut his male clients' hair in the men's lavatory, and to his present location in a building on Green Street where he also keeps a flat. Kingsley opened his New York office nearly five years ago and now spends nine months a year on this side of the Atlantic.

Kingsley traces most problems to blow-drying, coloring and even brushing. "People are still going to do those things," he allows, but he advises that the correct way to blow-dry hair is to leave it "fractionally damp. The last 10 seconds make a difference." He also warns against brushing, which, he says, "can cause hair loss from pulling the hair from the follicle." As for coloring and perming, both remove moisture, and although each in itself is not overly damaging, "the combination," says Kingsley, "is awful. No hairdresser should do both in the same day." He advises perming first, coloring second.

Kingsley, by the way, has a healthy head of reddish-brown hair and devotes 25 minutes a day to tending his locks. "Hair problems sneak up on you," he warns those who scoff at his suggestion of yearly visits to a trichologist. "Just remember, nobody waits until his teeth fall out before he sees a dentist."