I would be more concerned about Epson salts 🙂 I mean if you take supplements, soak in Epsom salts (Magnesium) and use a topical mayyybbeee it could add up but it seems like a cream for your foot would be fine. If you are nervous, make sure you have calcium too- I was told. Would a nurse at your doctor's office or a pharmacist be reassuring? We are lay people here and I am only sharing my experience.