What do SPF and PA mean for sunscreen? The higher the value, the better.

We buy sunscreen in the summer. There is a number on the sunscreen. So what do SPF and PA mean? Are higher SPF and PA numbers in sunscreen better?

What do SPF and PA mean in sunscreen?

Sun Protection Factor (SPF) refers to the SPF sun protection factor, which is a detection index that measures the ability of sunscreen to defend against ultraviolet UVB in sunlight, indicating the level of sun protection effectiveness that sunscreen products can provide. It is determined based on the minimum erythema dose to the skin. The coefficient after the SPF value refers to the time range within which ultraviolet radiation will not cause damage to the skin. The sun protection factor for protection against UVA is expressed as PA or PPD.

The minimum erythema dose is the shortest sun exposure time at which erythema appears on the skin. After using sunscreen products, the minimum erythema dose of the skin will increase, so the sun protection factor SPF of the sunscreen products is: SPF = minimum erythema dose (after using sunscreen products) / minimum erythema dose (before using sunscreen products)

PA stands for the ability to inhibit UVA from causing skin aging, collagen loss, and skin cancer. The more plus signs there are, the stronger the defense capability.

Are higher SPF and PA values ​​for sunscreen better?

Although SPF is an important indicator of sun protection, it does not mean that the higher the SPF value, the stronger the protection. Sunscreen is not long-lasting. The higher the SPF, the more chemical sunscreen is added. This type of sunscreen is corrosive. The more you add, the more corrosive it becomes. Too much sunscreen can easily penetrate into the skin and cause allergies and other problems. [6] For example, SPF15 has a protection rate of 93%, while SPF34 only has a protection rate of 97%. However, the larger the SPF value, the worse its permeability, which will hinder the normal secretion and breathing of the skin.

The defensive effect of PA is divided into three levels, namely PA+, PA++, and PA+++. PA+ means effective, PA++ means quite effective, and PA+++ means very effective. The more + signs, the stronger the ability to resist UVA. However, products with high sunscreen factors often contain large amounts of physical or chemical sunscreens, which are more irritating to the skin, easily clogging pores, and even causing acne and blackheads.

PFA<2 has no effect in protecting against UVA; PFA2-3, PA+; PFA 4-7, PA++; PFA≥8, PA+++.

Did you know that the higher the SPF and PA values ​​of sunscreen, the better.