Human skin becomes dry during winter, making it more prone to infections than during summer. how do the sebaceous glands protect the skin normally? a. sebaceous glands produce a substance that moisturizes and protects the skin. b. sebaceous glands cause the hair to stand erect, which insulates and protects the skin. c. sebaceous glands produce keratin, which gives the skin a tough structure and protection. d. sebaceous glands contain collagen fibers, which provide strength and protection.