How can I avoid microcystic chin acne in hot, humid weather?

The best proven strategy to prevent acne including chin acne is the regular use of prescription topical medication known as topical retinoids. This includes topical tretinoin e.g. retin-A, stieva A, retacnyl and topical adapalene e.g. differin. Such creams should be used even when no obvious acne is present. Topical retinoids act by unclogging the opening of the oil glands and preventing the formation of microcomedones which is the start of acne.