Besides causing a mild burning during the first few applications (or severe burning if accidentally placed in sensitive areas, such as the eyes), side effects are few with the use of capsaicin cream.⁶ As with anything applied to the skin, some people may have an allergic reaction to the cream, so the first application should be to a very small area of skin. Do not attempt to use capsaicin cream intra-nasally for headache treatment without professional guidance.

When consumed as food—one pepper per day for many years—cayenne may increase the risk of stomach cancer, according to one study.⁷ A different human study found that people who ate the most cayenne actually had lower rates of stomach cancer.⁸ Overall, the current scientific evidence is contradictory. Thus, the relationship between cayenne consumption and increased risk of stomach cancer remains unclear.⁹ Oral intake of even 1 ml of tincture three times per day can cause burning in the mouth and throat, and can cause the nose to run and eyes to water. People with ulcers, heartburn, or gastritis should use any cayenne-containing product cautiously as it may worsen their condition.