You wouldn't be alone if you think "orange juice" at the mention of vitamin C. The nutrient abundant in citrus, also known as ascorbic acid, is critical to forming our blood vessels, cartilage, muscles and production of collagen.

Vitamin C also helps us heal wounds and protect cells from the harmful effects of free radicals, the molecules created from sources such as the sun or tobacco smoke. The body doesn't produce the vitamin, so it's a requirement in a balanced diet.

But is a vitamin C serum required for a healthy skin care routine? Let's look at the benefits of vitamin C serums to see if they are a good choice for your skin and skin care goals.

What are the benefits of vitamin C when it comes to our skin?

If you spend any time on social media, you may already be aware that vitamin C gets hyped as a workhorse skin care ingredient that can both correct and prevent issues. As the most plentiful antioxidant in the skin, vitamin C plays a part in maintaining healthy skin.

"Vitamin C actually works in lots of different ways," says Annie Christenson, a medical aesthetician at Houston Methodist. "It helps to repair sun damage that has already happened, and it protects against future sun damage."

Skin damage can occur due to the aforementioned free radicals from UV rays. These free radical molecules have at least one set of unpaired electrons, which causes them to try and bond with other atoms, electrons or molecules. This damages the skin by lowering its levels of vitamin C. Applying vitamin C will give the free radicals an electron to pair with, rendering them harmless to your skin.

With its ability to protect against the sun, vitamin C can combat skin issues such as hyperpigmentation, where the skin has patches of darker skin, also called dark spots or sun spots. This is because vitamin C can help curb the production of melanin, another player in the development of some of these issues that affect the skin's tone and overall appearance.

Vitamin C is also known to help reduce wrinkles due to its involvement in stimulating collagen production. As we age, we produce less collagen and connective tissue, which can accelerate the signs of aging. Vitamin C can help you maintain the collagen you do have, while encouraging new growth.

Vitamin C's role in wound healing also can help lower the risk of scarring, including acne scars.

"Everybody can benefit from using vitamin C," Christenson says. "The only problem is it sometimes can be irritating to the skin, so if you have more sensitive skin, you have to be careful using it and find a formula that works for you."

Types of vitamin C serums and skin care — and why they matter

If you're interested in the benefits of vitamin C for the skin, you're in luck. There's a host of products, whether serums, oils, creams, masks or sunscreens, that are vehicles to get vitamin C to your skin. But the type of vitamin C, the concentration and factors such as storage can affect how much of a benefit you get from a product.

Vitamin C is an unstable molecule, meaning it is water soluble and breaks down when exposed to oxygen. This breakdown can affect whether the skin can effectively absorb the product. L-ascorbic acid is sensitive to high heat, high pH or sunlight. This can lead to a shorter shelf life, especially if stored incorrectly.

Other types of vitamin C, including magnesium ascorbyl phosphate, sodium ascorbyl phosphate, tetrahexyldecyl ascorbate and tetraisopalmitoyl ascorbic acid, are often paired with ingredients such as vitamin E and ferulic acid. This stabilizes the vitamin C, helping with shelf life and the absorbability of the product.

Selecting vitamin C products that include these stabilizing ingredients can help ensure you're getting an effective product. Plus, vitamin C products paired with vitamin E and ferulic acid may be easier for people with sensitive skin to tolerate and use.

How to pick an effective vitamin C serum

Christenson says that the type of vitamin C serum or product you use can come down to personal preferences, including what feels good on your skin and what works well with your other products or prescriptions. Any vitamin C serum or product you choose should be comfortable to wear and use with your other skin care.

"I like a vitamin C that is generally a serum or lightweight gel, something thinner that's going to penetrate," Christenson says. "I think you're going to get a more concentrated product that way."

When shopping for a vitamin C serum or other product, take note of the following criteria:

• Packaging: Any vitamin C product packaging should be dark or tinted, with a preference for a pump rather than a dropper. With vitamin C being sensitive to heat and light, packaging can help your product last longer, especially if you're storing it in a bathroom that occasionally can be humid.
• Opt for a brand that uses clinical testing: Pay attention to whether the brand conducts clinical testing and has any tests regarding the product to back its claims. Vitamin C serums and products don't come cheap — going with a brand and product with testing behind it may help you select an effective product.
• Pay close attention to the concentration: Vitamin C in most serums and products is anywhere from 10% to 20%, so those with sensitive skin may want to use products at a lower concentration. If you have extremely sensitive skin or a condition such as rosacea, you're going to want to work with your dermatologist or skin care professional to choose a product that will work for you.
  
  

How to incorporate vitamin C into your skin care routine

You've picked a product you like. Now, how do you use it?

To make sure you're applying your products correctly, Christenson says to pay attention to each product's viscosity — a fluid's resistance to flow. The higher the viscosity of a product, the thicker it is.

"So a couple rules of thumb — you're always going to wash your face first with your cleanser," Christenson says. "Then, apply the lightest, thinnest product first. So, if you use a toner or other very thin, liquid product, it may be first. Then you'd put on any lightweight gel or serum. If you have any heavier creams you use, that would be next. And, of course, your sunscreen is always the last product used during the day."

It is OK to use both vitamin C and a retinoid, a prescription-strength vitamin A skin care product, or a retinol, an over-the-counter vitamin A product. To ensure you're getting the full benefits of both your vitamin A and C products, you'll want to use them at different times.

"Certain products are better used at different times of the day," Christenson says. "Generally, vitamin C should be used during the daytime to help protect against the sun, and you'd use your retinol exfoliating vitamin A at night. Using a vitamin C product at night will not benefit you as much as it will during the day."

Plus, to avoid wasting your money, Christenson says you should follow the instructions of your products.

"If the directions say to use one dropper or one pump of the product, then use that amount for each area treated," Christenson says. "So, one dropper or pump for the face, one for the neck and one for the décolleté. The recommended amount is best for the penetration of the product and is most economical."