I read somewhere that after giving birth it's not advisable to use cos…

I read somewhere that after giving birth it's not advisable to use cosmetics. Not shower gels, not makeup, not perfumes, not deodorants. It's said that all of this can cause allergies in the baby. Is it true or not? I just always dye my hair red and before giving birth I didn't have time to get it done so now I'm not red but pale even looking at myself in the mirror is scary... That's why I'm thinking if I can paint it again and use all other cosmetics?