Menstrual cramps respond to essential oils especially when used in a warm
bath with Epsom and Sea Salt.
Essential Oils useful for cramps are:

Chamomile
Cypress
Basil
Carrot Seed
Frankincense
Clary Sage
Juniper
Jasmine
Lavender
Marjoram
Nutmeg
Peppermint
Rosemary

Here's a recipe from Valerie Cooksley
5 drops Lavender 2 drops Cypress 2 drops Nutmeg 2 drops Peppermint add to
bath salts, soak for 20 min. Rest afterwards, elevating your legs.