Before using tretinoin, tell your doctor or pharmacist if you are allergic to it; or to vitamin A-related drugs (other retinoids such as isotretinoin); or if you have any other allergies. This product may contain inactive ingredients (such as fish proteins), which can cause allergic reactions or other problems. Talk to your pharmacist for more details. During the first few weeks of using tretinoin, your acne might appear worse because the medication is working on pimples forming inside the skin. It may take up to 8-12 weeks to notice results from this medication. This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Weather extremes such as wind or cold may also be irritating to the skin. Use sunscreen daily and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness. Wait until your skin has completely recovered from a sunburn before using tretinoin. This drug may pose risks to your pregnancy, therefore please do not take this medicine without consulting your doctor first. Ask your dermatologist before using it.