SPF X PPD
The effectiveness of a sunscreen is measured by its ability to protect the skin from ultraviolet rays: A (PPD) and B (SPF). The SPF (Sun Protection Factor) purpose is to filter UVB rays, which penetrate the top layer of skin causing redness and burning and may be responsible for skin cancer.
The PPD (Persistent Pigment Darkening) filters UVA rays, which penetrate into the deeper layers of the skin, and can cause sun damage and darkening of the skin, accelerating the aging process and also causing changes that can lead to skin cancer.
Dermatologists recommend that at the beach and at the pool, where sun exposure is intense, sunscreens with an SPF above 50 and above 15 PPD are the ones that offer better protection. On a daily basis, if the person is not going under any skin treatment, a sunscreen with SPF 30 or higher is enough.
Applying sunscreen frequently is the big secret. It seems obvious, but most people do not have this habit. The first step is to apply it at least 30 minutes before leaving the house and that includes even those products that say “immediate protection” on the label. During prolonged sun exposure, re-apply every hour and a half or two hours and specially after diving or sweating excessively. Even so, the recommendation is to make use of other allies in the battle against the sun: staying under the umbrella, wearing a hat and a shirt, sunglasses and avoiding exposing at the times the sun is very strong.
Face and body
Face and body sunscreens have different properties. The body sunscreens are usually more liquid to enhance its spreadability. They may have a milder effect if used on the face, reducing its actual protection. Also, the formulation may be inappropriate for the face and it may clog the skin and cause blackheads. It is ideal to apply a face sunscreen as oil-free as possible, especially those with oily skin. If not possible, the use of hats or visors is more appropriate than a filter that is not oil-free.