OMG MY HANDS ARE SO DRY! i put lotion on every day many times a day!! help!!?

i have this thing called "exem" or something, idk what its called in english but its like when your really cold or get in touch with strong chemicals, then your skin gets really dry and red :S WHAT CAN I DO!?!? ive tried soo many lotions or something from doctors but it only makes it worse!!