There is no doubt a sun-kissed, summertime glow will boost your confidence and make you look and feel healthier.

But, like all good things, the sun is good only in moderation, as dangerous UVA and UVB rays can lead to skin cancer.

So, how do you recognize the signs of skin cancer, especially since humans always have some sort of pre-existing beauty mark, mole or sun spot?

“The way to be aware of it is the ABCDs,” said Dr. Jody A. Levine, a dermatologist from Plastic Surgery & Dermatology of NYC. They are:

A – Asymmetry

B – Border irregularity

C – Color variety

D – Diameter greater than 5 millimeters

“If you have a dark mark on your skin, look for a change in its color, shape or size over the course of several months,” Levine said. “The types of things that make you nervous are the ABCDs. If you drew a line down the middle, would it be irregular on one side? Is the border not smooth? Look at the color variety. You might see some pink spots, or black spots and some brown spots in it. The diameter is based on size. We all have beauty marks, but if it becomes large, you should be concerned.”

Click here to see pictures of the ABCDs of skin cancer.

There are three types of skin cancer, Levine said:

— Basal cell carcinoma. This is the most frequent type of cancer. They are growths on the skin that can be red or scaly, or even look like a pimple. It may bleed or look like a cut that isn’t going away.

— Squamous cell carcinoma. Like basal cell carcinoma, this is usually a non-aggressive type of cancer, but it can metastasize if it starts on a mucous membrane such as the lips or eyes.

— Melanoma. Melanoma is the deadliest form of the three. One-fifth of patients develop metastatic disease, which is usually associated with death.

Are You at Risk?

Any mark on the skin that cannot be attributed to a specific cause should be looked at.

If you have had actinic keratosis, or precancerous skin lesions; have a family history of skin cancer; or if you have many moles on your body, than you may be at risk for skin cancer, Levine said.

“Early detection and appropriate excision leads to a cure rate of more than 90 percent in low-risk melanoma patients,” she added.

The best way to avoid skin cancer is to avoid midday sun, Levine said, but that isn’t always practical. So people are advised to wear protective clothing like wide-brimmed hats and long-sleeves, and always using a sunscreen that has both UVA and UVB protection.

“I never use anything less than an SPF 30,” Levine said. “But the key is to apply enough of it so that you are getting the number on the bottle. And, make sure to reapply every two to three hours.”

And remember – even if you aren’t getting sunburned, you can still be receiving the harmful effects of the sun, Levine said.

“There are two different types of sun rays,” she said. “UVB is the type that leads to burning, and some of the non-melanoma skin cancers. UVA penetrates deeper than UVB, so while they don’t cause burning, it does lead to melanoma and aging of the skin.”

Click here to learn more about skin cancer from the American Academy of Dermatology.