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Haircuts and hairstyles can make you look a lot younger. There is no one way to wear your hair to look mature. However, there are things you can avoid so you don't look young. Don't dye your hair crazy colors or place colored streaks in them. Shy away from extreme hairstyles, like mohawks, half-shaved heads, and dreadlocks. Wear your hair in a conservative manner.  Shaggy hair makes a guy’s face look much younger. Replace it with a short, defined cut.  Spiked hair, long hair, or any other alternative hairstyle might make you look younger. For women, think about cutting your hair into a bob, pixie cut, or other chic hairstyle. Long, sleek hair can also look mature. Avoid wearing lots of hair accessories, like hairbands, hair bows, and scrunchies. For a guy, growing facial hair can make you look older and more mature. A recent study found that beards can make a man look up to 10 years older. If you decide to grow facial hair, make sure it is a good look on you. Some teenage boys can't grow enough facial hair to have goatees or beards.  Make sure to trim and groom your facial hair. Messy, unkempt beards look bad. If it grows in thinly, keep yourself clean-shaven. Uneven patches of facial hair will make you look even younger. wear makeup, which can add years to your face. Use eyeliner to outline your eyes. Wear neutral colors, like golds and browns. Don't wear bright or pastel colors. Add some foundation to smooth out your skin.  Conceal the circles under your eyes with concealer.  Avoid teenage products like thick, sparkling lip gloss or baby-pink nail polish. Appearing to have clear skin will definitely add maturity to your face. Use a spot concealer to cover acne. Adopt a healthy skin care regiment. Try over the counter acne products, like spot creams and cleansing wipes.  Wash your face twice a day with an acne cleansing face wash. Use a moisturizer on your skin. If you have oily skin, use an oil-free moisturizer. If you have dry skin, find one that helps fight dry skin.  If you’re a girl, you might wear bangs in addition to makeup to hide blemishes on your forehead. This will not only help combat baby fat, but also add muscle definition, which definitely helps teens look older. Guys might want to focus on upper body exercises to broaden their shoulders and build their arms. Girls might want to trim their waists and develop their chest and butt muscles to accentuate their womanly curves.  Interval training is an excellent way to burn fat quickly and using hand weights will help develop muscle. Join a gym or focus on exercises like push-ups and squats that build muscle.
Wear a mature haircut. Grow facial hair. Wear light makeup. Cover your acne. Work out.