Is it ok to take the prenatal vitamins after finishing lactating? these vitamins have help for my severe allergy?

YES: It is perfectly safe to take prenatal vitamins any time until menopause (after menopause it is best to avoid taking vitamins with iron). Most prenatal vitamins are well-rounded multivitamins. I am happy to hear they have helped your allergy, consider adding extra vit. C (1-2, 000 mg 2x/day) extra b5 (500 mg 2-3x/day) and consider trying stinging nettles extract and quercitin as well.

Vitamin supplements: Prenatal vitamins have higher level of folic acid, iron and calcium than regular vitamins. It should be fine if you continue to take it except from a few medical conditions that you cannot eliminate iron. It should not affect your allergy symptoms since it does not have any anti allergy properties.