If someone has a problem using meth amphetamines could it cause them to get cellulitis. what would cause it? needles? is cellulitis contagious

Yes: skin puncture can cause skin infections leading to abscess and/or cellulitis. It can be contagious if the needle is shared. Contaminated needles and drugs can also cause it

Generally needles: methamphetamine is frequently injected, although smoking is the dominant form of use (free base methamphetamine or "crank" or "ice"). Cellulitis is an infection under the skin that can often lead to abscess or spread of infection. However, poor personal hygiene is notorious in heavy methamphetamine users and that can also contribute to developing celluliis. It's not contagious.

Of course: Methamphetamine may cause side effects including skin problems like dermatitis and cellulitis. See your PCP for evaluation and proper addiction treatment referral.