Pepper

If you think pepper is pepper and what could go wrong, think twice.

Pepper usually comes in either whole corn or ground form.

Ground pepper should be avoided as it may contain fillers. You will never know if whoever ground it in some third-world country "stretched" it a bit with dirt, sawdust, <fill in your evil substance> just to make some more money.

Whole pepper corn mixes, i.e. those with differently colored pepper corns, should be avoided as well. The red pepper corns could be Schinus molle or Schinus terebinthifolia. The latter one is preferred by spice merchants and may cause allergies (3/4 of people in the US south are allergic to contact, cross allergies with cashew nuts).

Use whole black pepper corns only and grind them when needed.

Black Pepper helps to fight malaria.