Sunscreens are effective at protecting the skin from the harmful effects of the sun's ultraviolet (UV) rays. UV radiation is a known cause of skin cancer and can also cause premature aging of the skin. Sunscreens work by absorbing, reflecting, or scattering UV rays, which helps to protect the skin from the damaging effects of the sun.

There are two types of UV radiation: UVA and UVB. UVA rays are longer wavelengths that can penetrate deep into the skin and cause premature aging and wrinkling. UVB rays are shorter wavelengths that are more likely to cause sunburn and skin cancer. Both types of UV radiation are harmful to the skin, and it is important to protect yourself from both.

Sunscreens are rated based on their sun protection factor (SPF), which is a measure of how well they protect the skin from UVB rays. A higher SPF rating means that the sunscreen is more effective at blocking UVB rays and preventing sunburn. However, it is important to note that no sunscreen can completely block all UV radiation, and it is still important to take other precautions, such as seeking shade and wearing protective clothing, to reduce your risk of sun damage.

How to choose a sunscreen?

There are a few factors to consider when choosing a sunscreen:

1. Sun Protection Factor (SPF): The SPF rating indicates how well the sunscreen protects against UVB rays. A higher SPF rating means more protection. It is recommended to use an SPF of at least 30.

2. Broad-spectrum coverage: Choose a sunscreen that provides broad-spectrum protection, meaning it protects against both UVA and UVB rays.

3. Water resistance: If you will be sweating or swimming, choose a sunscreen that is water-resistant.

4. Skin type: Choose a sunscreen that is suitable for your skin type. If you have sensitive skin, look for a sunscreen that is labeled "sensitive skin" or "for sensitive skin."

5. Ingredients: Some people may be sensitive or allergic to certain ingredients in sunscreens. If you have sensitive skin or allergies, look for a sunscreen that is free of fragrances and other potential irritants.

6. Formulation: Sunscreens come in different formulations, such as lotions, creams, sprays, and sticks. Choose the formulation that you are most comfortable using.

7. Price: Sunscreens can vary in price. Choose a sunscreen that fits your budget, but be aware that cheaper sunscreens may not always offer the same level of protection as more expensive brands.

 Frequently found ingredients in a sunscreen - 

The active ingredients in sunscreens are the ones that provide the sun protection. Some common active ingredients found in sunscreens include:

1. Avobenzone: A chemical sunscreen that absorbs UVB and short-wavelength UVA radiation.

2. Octinoxate: A chemical sunscreen that absorbs UVB radiation.

3. Octocrylene: A chemical sunscreen that absorbs UVB radiation.

4. Oxybenzone: A chemical sunscreen that absorbs UVB and UVA radiation.

5. Titanium dioxide: A physical sunscreen that reflects and scatters UV radiation.

6. Zinc oxide: A physical sunscreen that reflects and scatters UV radiation.

In addition to the active ingredients, sunscreens may also contain a variety of other ingredients such as fragrances, preservatives, and emollients. It is important to read the ingredient list and choose a sunscreen that is suitable for your skin type and any allergies or sensitivities you may have.