ANSWER: Let us first begin with a definition before we tackle the issue of sin. What we commonly refer to as makeup are various substances and chemical compounds people wear for the express purpose of enhancing their appearance.
In modern times, the use of cosmetics (makeup) is not limited to females, or to being applied only to the face (non-facial scars or birthmarks are sometimes covered), or used only by adults (teenagers sometimes use them to cover the effects of acne).
Without a doubt, makeup has been a hotly debated, and many times divisive, topic among churches and fellowships. Some women have even been ejected from church services (and told never to come back) because they dared to wear cosmetics. Discussions centering on whether the use of makeup, which is not clearly delineated in Scripture, are acceptable or not (a sin) have raged for quite a while.
"During the past several generations some of the strongest debate among fundamentalists and evangelicals (regarding sin) has centered around questionable practices . . . Some of the key issues have been drinking alcoholic beverages, smoking, card playing, wearing makeup . . ." (MacArthur New Testament Commentary on 1Corinthians).
It should be noted that English words such as "makeup" or "lipstick" are not found in Scripture. Direct references to the use of cosmetics are somewhat rare in the Old Testament, occurring only four times (2Kings 9:30, Isaiah 3:14 - 16, Jeremiah 4:30 and Ezekiel 23:40). The first Biblical reference involves former Israelite Queen Jezebel "painting her face" (applying makeup) in order to try to win the favor of Jehu, the newly anointed king of Israel (2Kings 9:1 - 6, 30). Her attempt to win favor, however, failed miserably (verses 32 - 37).
We need look no further than the creation of man for a guiding principle regarding whether or not it is a sin to wear makeup.
The Bible states that God made everything, including humans and the Garden of Eden, "exceedingly good" (Genesis 1:31, HBFV throughout). He then placed Adam (and soon Eve) in the garden with the express purpose that they "dress it and keep it" (verse 15). What did he, however, expect them to do since everything around them was unspoiled and did not so much as contain a single weed (weeds would grow AFTER sin entered the picture, see Genesis 3:17 - 18)?
God's will was that the first man and woman use their creativity to change and build upon what they were given. Rather than commanding they leave everything untouched (since it was already "good"), he expected and desired that they alter (guided by righteousness and wisdom) the garden to expand and further beautify it as they saw fit. Enhancing what the Eternal made was not wrong. Based upon this principle, it is not a sin if a woman uses makeup to enhance her appearance and the natural beauty she has received.
New Testament admonitions
What we find in the New Testament is NOT a condemnation of makeup as a sin but rather admonitions regarding its proper place and priority in a person's life. The Apostle Paul encourages Christian women to dress modestly and not draw unnecessary attention to themselves by how they look. Though makeup and cosmetics in general are not forbidden, emphasis should be placed far more on doing good than looking good (1Timothy 2:9 - 10). Peter also admonishes females (especially those married) to place their primary focus not upon how they look but rather on manifesting a righteous character (1Peter 3:3 - 4).
Wearing makeup (like drinking alcohol) is a question of moderation rather than prohibition. While it is certainly not wrong to forego cosmetics, using them with wisdom and modesty is not a sin. It would be wrong, however, to use them for the express purpose of leading another person to lust and disobey God in their heart. Believers should always be mindful how what they say, and do, will be perceived by others (1Thessalonians 5:22 - 23).