As a herbal tea, rosemary tea is generally safe, but if you drink too much, it may have some side effects, including:

1. Stomach upset: Drinking too much rosemary tea may cause stomach upset, such as stomach pain, nausea and vomiting.

2. Increased stress: Excessive rosemary tea may lead to increased physical stress, causing problems such as rapid heartbeat, anxiety and insomnia.

3. Drug interaction: Rosemary tea contains some chemical components, which may affect the action of some drugs, such as antihypertensive drugs and heart drugs.

4. Allergy: Individuals may be allergic to some ingredients in rosemary tea, which may lead to allergic symptoms such as itchy skin, burping and sore throat.

Therefore, we suggest drinking rosemary tea in moderation, generally no more than 3 cups a day. If you feel unwell, stop drinking immediately and consult a doctor.