Melatonin is a hormone that helps regulate sleep-wake cycles. It is commonly used as a supplement to treat sleep disorders such as insomnia. While melatonin is generally considered safe, it can have some side effects that individuals should be aware of.

1. Drowsiness: One of the most common side effects of melatonin is drowsiness. Since melatonin is primarily used to promote sleep, it can cause excessive sleepiness, especially if taken during the day or in higher doses. Individuals should avoid driving or operating heavy machinery until they know how melatonin affects them.

2. Headaches: Some individuals may experience headaches after taking melatonin. This side effect is usually mild and temporary. If headaches persist or become severe, it is advisable to consult a healthcare professional.

3. Nausea and Upset Stomach: Melatonin can sometimes cause gastrointestinal symptoms such as nausea, stomach cramps, or diarrhea. These side effects are typically mild and resolve on their own. If they persist or worsen, it is recommended to seek medical advice.

4. Mood Changes: In rare cases, melatonin can cause mood changes such as increased irritability, anxiety, or even depression. If these symptoms occur or worsen, it is important to consult a healthcare provider.

5. Vivid Dreams or Nightmares: Melatonin can affect the content and intensity of dreams. Some individuals may experience more vivid dreams or even nightmares while taking melatonin. These effects are generally harmless and temporary.

6. Blood Pressure Changes: Melatonin can potentially affect blood pressure levels. It may lower blood pressure in some individuals, which can be beneficial for those with hypertension. However, individuals with low blood pressure should exercise caution and monitor their blood pressure regularly while taking melatonin.

7. Allergic Reactions: Although rare, some individuals may experience allergic reactions to melatonin. Symptoms may include rash, itching, swelling, dizziness, or difficulty breathing. If any signs of an allergic reaction occur, immediate medical attention should be sought.

It is important to note that individual responses to melatonin can vary, and not everyone will experience these side effects. If you have any concerns or questions about melatonin or its side effects, it is always recommended to consult a healthcare professional.

References:

1. Mayo Clinic. (2021). Melatonin: Side effects. Retrieved from https://www.mayoclinic.org/drugs-supplements-melatonin/art-20363071
2. National Sleep Foundation. (n.d.). Melatonin and Sleep. Retrieved from https://www.sleepfoundation.org/nutrition/melatonin-and-sleep