พอดีไปเจอ web ที่มีเนื้อหาเกี่ยวกับกันแดด อ่านแล้วเนื้อหาน่าสนใจดี เลยเลือกบางส่วนมาให้อ่านกัน ถ้าใครขี้เกียจหรือไม่เก่งภาษาอังกฤษ (เหมือนเราเลย) ก็ข้ามไปอ่านช่วงสุดท้ายเลยก็ได้ เพราะว่ามีบอกว่าสารอะไรที่อยู่ในกันแดด และกันรังสีอะไรได้บ้าง


ส่วนใหญ่คนจะห่วงเรื่อง spf แต่ไม่ห่วงเรื่อง pa ซึ่งจะช่วยกัน UVA ทั้งๆ ที่ uva เนี่ยมันทำลาย collagen ในผิว ทำให้ผิวแก่กว่าวัยได้ ในขณะที่ uvb จะทำให้ผิวไหม้ ยังไงคราวหน้าเวลาเลือกซื้อกันแดด ก็ให้พิจารณาด้วยนะคะ


What SPF should I use?

Sunblock protects your skin by absorbing and/or reflecting UVA and UVB radiation. All sunblocks have a Sun Protection Factor (SPF) rating. The SPF rating indicates how long a sunscreen remains effective on the skin. A user can determine how long their sunblock will be effective by multiplying the SPF factor by the length of time it takes for him or her to suffer a burn without sunscreen.

For instance, if you normally develop a sunburn in 10 minutes without wearing a sunscreen, a sunscreen with an SPF of 15 will protect you for 150 minutes (10 minutes multiplied by the SPF of 15). Although sunscreen use helps minimize sun damage, no sunscreen completely blocks all wavelengths of UV light. Wearing sun protective clothing and avoiding sun exposure from 10 a.m. to 3 p.m. will also help protect your skin from overexposure and minimize sun damage.

SPF, PA and UV Protection explained

SPF (Sun Protection Factor UVB) measures the length of time a product protects against skin reddening (sunburn) from UV (Ultra Violet) radiation, compared to how long it takes to redden without protection. If it takes 30 minutes without protection to begin reddening, using an SPF-18 sunscreen prevents reddening 18 times longer. An SPF-18 blocks 95% of UV rays, while an SPF-30 blocks only 2% more.

PA (Protection Grade UVA) is the expression for UVA Protection, based on the Persistent Pigment Darkening (PPD) test method.
Indications on label:

PA+        UVA Protection
PA++     Considerable UVA Protection
PA+++   Greatest UVA Protection

What is the best type of sunblock to purchase?

The best sunblock varies from individual to individual. We recommend broad spectrum sunblock with UVA and UVB protection, a SPF rating of at least 30, in a form that is gentle enough for daily use.

Active ingredients of sunblock vary from manufacturer to manufacturer and can be divided into chemical versus physical agents. Chemical sunblocks work by absorbing the energy of UV radiation before it affects your skin. Physical sunblocks reflect or scatter UV radiation before it reaches your skin. Some sunblocks combine both chemical and physical sunblocks.

The two types of physical sunblocks that are available are zinc oxide and titanium dioxide. Both provide broad spectrum UVA and UVB protection and are gentle enough for everyday use. Because these are physical blocking agents and not chemicals, they are especially useful for individuals with sensitive skin, as they rarely cause skin irritation.

Most chemical sunblocks are composed of several active ingredients. This is because no single chemical ingredient blocks the entire UV spectrum (unlike physical sunblocks). Instead, most chemicals only block a narrow region of the UV spectrum. Therefore, by combining several chemicals,with each one blocking a different region of UV light, one can produce a sunblock that provides broad spectrum protection. The majority of chemical agents used in sunblock work in the UVB region. Only a few chemicals block the UVA region. Since UVA can also cause long-term skin injury, dermatologists at UCSF routinely recommends sunblocks that contain either a physical blocking agent (e.g. titanium dioxide or zinc oxide) or Avobenzone (also known as Parsol 1789).

Sunblocks comes in a variety of forms. Lotions, oils, sticks, gels, sprays and creams can all be effective sunscreens. However, sunblocks are only effective if they are used. We encourage you to try several types and find the one which works and feels the best to you. All sunscreens should be applied 15-20 minutes before sun exposure to allow a protective film to develop, then reapplied after water contact and sweating. Some sunblocks can lose effectiveness after two hours, so reapply frequently.

In general, spray lotions and gels are the least oily but also the ones that wash off more easily and need to be reapplied more frequently. If you develop a rash or other type of allergic response to a sunscreen, try a different brand or form (lotion vs. oil, for example) to see if you can better tolerate it. The most common allergic reactions occur with sunscreens that contain PABA-based chemicals. If you develop a rash to a sunblock, check the label to see if PABA is an ingredient. If so, consider avoiding sunblocks that contains this in the future. Alternatively, try a titanium dioxide or zinc oxide containing sunblock as they rarely cause skin irritation and provide very good broad spectrum UV protection.

Water resistant sunblocks are available for active individuals or those involved in water sports. It's important to check the label to ensure they say "water-resistant" or "very water-resistant."

Water-Resistant sunblock maintains the SPF level after 40 minutes of water immersion
Very Water-Resistant sunblock maintains the SPF level after 80 minutes of water immersion


ส่วนตรงนี้เนี่ย เอาไว้ดูว่ากันแดดตัวไหนกันรังสีอะไรได้บ้างนะคะ เมื่อกี้เราลองเอาข้างขวดกันแดดที่เรามีอยู่มาเทียบ ก็มีอยู่ 3-4 ตัว กันได้ทั้ง UVA, UVB มีประโยชน์มากค่ะ

Common active ingredients of sunblock and the type of UV light blocked:

UVA ("the aging ray") and UVB ("the burning ray")

Active Ingredient       Type of UV radiation blocked
Aminobenzoic acid      UV-B
Avobenzone               UV-A  
Cinoxate                    UV-B
Dioxybenzone             UV-B, UV-A
Homosalate                UV-B
Menthyl anthranilate    UV-A
Octocrylene                UV-B
Octyl methoxycinnamate  UV-B
Octisalate                   UV-B
Oxybenzone                UV-B, UV-A
Padimate O                 UV-B
Phenylbenzimidazole sulfonic acid UV-B
Sulisobenzone             UV-B, UV-A
Titanium dioxide          UV-A/B, broad spectrum
Trolamine salicylate     UV-B
Zinc oxide                   UV-A/B, broad spectrum


http://www.dermatology.ucsf.edu/skincancer/General/prevention/Sunscreen.aspx

ใครเก่งอังกฤษว่างๆ ก็ช่วยแปลหน่อยนะคะ