Procter & Gamble Co. has said that it bought HDS Cosmetics Lab Inc., the company that manufactures and markets the Doctor’s Dermatologic Formula skin care line. The Cincinnati-based consumer products company bought HDS Cosmetics from North Castle Partners, a private equity firm based in Greenwich, CT. The companies did not disclose details of the transaction. The Doctor’s Dermatologic Formula line includes products for anti-aging, acne, hyper-pigmentation and sun protection. The products are sold in select spas and in specialty retail and department stores. P&G officials say the acquisition is part of its corporate strategy of focusing on skin care as a major growth category. Other brands acquired and grown by P&G include Pantene, Olay and Cover Girl. North Castle invested in Yonkers, N.Y.-based HDS Cosmetics Lab in 2004. The skin care line was created in 1991 by New York City dermatologist Dr. Howard Sobel.