Sometimes, sudden adult breakouts are caused by developing allergies to products or foods, even if you’ve used them before. This is because as we age, our skin becomes thinner and more sensitive. If you think something you’re eating might be causing your adult acne, consider keeping a food diary. If you notice a link between certain foods and skin blemishes, try eliminating that food for a couple of weeks and reevaluate. If you wear makeup or use skin lotions and beauty products, consider switching to a brand formulated for acne-prone or sensitive skin and see if that helps calm your skin issues, as well.