Prima uses all natural ingredients, so no side effects were reported so far. On the other hand, Prima is not recommended for vegans or vegetarians, as the capsules are coated with gelatin (the coating makes the capsules very easy to swallow).
Additional details about Prima Capsules
https://www.jpost.com/promocontent/prima-keto-uk-united-kingdom-is-it-scam-or-trusted-706402