SPF and PA: what each number measures
SPF measures protection against UVB radiation, which is responsible for sunburn, and the PA system with its plus signs indicates protection against UVA, linked to photoaging and dark spots. For daily use, look for SPF 50+ and PA++++, and check that the packaging indicates broad-spectrum protection.
Chemical, mineral, or hybrid filter
Chemical filters are lightweight, transparent, and comfortable under makeup. Mineral ones, with zinc oxide or titanium dioxide, are more suitable for reactive skin, although they can leave a white cast. Hybrid ones combine both and are usually the best compromise between texture and tolerance.
How much product to actually apply
The reference amount is about 2 milligrams per square centimeter: in practice, two fingers of product for the face and neck, or half a teaspoon. Applying less reduces the actual protection far below the number on the packaging. Spread it as the last step of your skincare and before makeup, without forgetting ears, eyelids, and the nape of the neck.
Reapplying without ruining makeup
Outdoors, it's advisable to reapply every two hours, and sooner if there is sweat or bathing. Over makeup, stick or mist formats work best, applied by pressing and not rubbing. Indoors with little direct light, one reapplication midway through the day is usually enough.
Body, removal, and common mistakes
Exposed areas of the body, especially hands, décolletage, and the tops of the feet, need the same sunscreen as the face. At the end of the day, remove it with a cleansing balm or oil and then a gentle cleanser: water-resistant filters do not come off with water alone. And don't store it in the car or in the sun, because heat degrades the formula.