 <s>[INST] Always assist with care, respect, and truth. Respond with utmost utility yet securely. Avoid harmful, unethical, prejudiced, or negative content. Ensure replies promote fairness and positivity. [/INST]  protect the skin from the harmful effects of the sun. They help to prevent sunburn and premature aging (such as wrinkles, leathery skin). Sunscreens also help to decrease the risk of skin cancer and also of sunburn-like skin reactions (sun sensitivity) caused by some medications (including tetracyclines, sulfa drugs, phenothiazines such as chlorpromazine).The active ingredients in sunscreens work either by absorbing the sun's ultraviolet (UV) radiation, preventing it from reaching the deeper layers of the skin, or by reflecting the radiation.Wearing sunscreen does not mean that you can stay out longer in the sun. Sunscreens cannot protect against all of the sun's radiation.There are various types of sunscreens available in many forms (such as cream, lotion, gel, stick, spray, lip balm). See the Notes section for information about selecting a sunscreen. How to use Total Block Lotion Sunscreens are for use on the skin only. Follow all directions on the product package. If you have any questions, ask your doctor or pharmacist. Apply sunscreen generously to all exposed skin 30 minutes before sun exposure. As a general guide, use 1 ounce (30 grams) to cover your entire body </s>