A yeast infection is caused by the overgrowth of a fungus called Candida albicans that already lives on you. There are several forms of yeast infection, vaginal being the most common, but skin yeast infection is another. If the immune system is already compromised by an existing condition it can make a person more prone to yeast infections. The skin is a large part of your immune system, conditions like psoriasis or lichen planus means your skin is weakened.
Any area that suffers irritation can be more prone to a yeast infection though it is more common in areas that the fungus thrives in, moist and warm. This means under the arms, under breasts, in the folds of skin in the obese and so on. If you are having a problem with recurring yeast infections (4 or more times a year) and you suspect your skin problems may be the reason for this you need to see your doctor. Talk to them about your suspicions and discuss treatment options. They may even put you on preventative anti-fungal medication.