Summarize this article:

When your lips are dry and chapped, they will appear thinner. You can make your lips appear plumper and healthier simply by taking better care of them; the first step to doing this is to drink enough water. A popular method for calculating how much water you should drink each day is to take your weight in pounds and divide it in half; the result is how many ounces of water you should drink each day. A 150-pound woman should drink roughly 75 ounces (about 2,200 ml) of water each day. When you lick your lips, your tongue spreads acidic saliva on them. This can remove your lips’ natural oils and cause them to become irritated. Smoking can irritate and discolor your lips; it can also cause wrinkles around your mouth. If you smoke and do not want to quit, at the very least try switching to an e-cigarette, which will not be as toxic to your lips as a regular cigarette. You may be able to reduce smoking-related discoloration by massaging almond and coconut oil on your lips each day. If your lips are dry or chapped, use a lip balm regularly. Even if your lips are not chapped, consider using a lip moisturizer that contains an SPF to protect your lips from the sun’s damaging rays.  If your lips are sensitive, it may take some trial and error to find a lip balm that works for you. Some people use natural balms containing ingredients like coconut oil and honey, while others find that medicated balms containing menthol are best. Unless your lips are already well-hydrated, avoid beeswax lip balms. Beeswax lip balms are too heavy to actually impart moisture to your lips; they can only seal in the moisture that’s already there. If you only put one thing on your lips, it should be SPF. The sun’s rays can cause your lips to chap and become dry, making them look smaller than they are.  Shiny products such as lip glosses can actually magnify the sun’s rays, causing them to harm your lips more than if you had nothing on your lips at all. Dermatologists warn that wearing lip gloss without an SPF can do more than damage your lips: it can actually cause skin cancer. Exfoliating your lips might help them feel smooth in the short term, but it can actually damage your lips if you do it regularly. Instead of exfoliating your lips, work on keeping them hydrated. Unlike your regular skin, your lips are made of a sensitive mucous membrane. When this membrane is healthy, it’s naturally smooth. If you are taking good care of your lips and they are still always chapped, you may be experiencing an allergic reaction to something you’re using on or near your lips:  Citrusy and salty foods can irritate lips. Some toothpastes can irritate lips. If you think your toothpaste may be causing problems for you, try switching to one that doesn’t contain sodium laurel sulphate or alcohol.  Be mindful of heavily scented facial products, which can wind up on your lips and can cause irritation.

Summary:
Drink enough water. You would need to drink more water if you lived in a hot climate or exercised — in other words, if you were sweating more than normal. Don’t lick your lips. Don't smoke. Apply a moisturizing balm to your lips. Wear SPF on your lips. Don’t exfoliate your lips. Avoid products that may cause allergic reactions.