Many believe Chinese herbs are purely natural with minimal or no side effects. However, recent studies indicate that overuse can harm the eyes and even cause severe vision loss. Exercise caution with the following herbs:
1. Licorice
Daily intake exceeding 50 grams may trigger toxic side effects.
One study found that five patients taking 186–746 grams of licorice daily experienced unilateral or bilateral flash blind spots and vision loss, accompanied by headaches and elevated blood pressure.
2. Ginkgo Biloba
Ginkgo is also one of the most commonly used Chinese herbs. Long-term combined use of ginkgo extract and aspirin can cause spontaneous anterior chamber hemorrhage in the eye. This occurs because both ginkgo and aspirin reduce platelet activity, and their combined effect increases the risk of bleeding.
3. Chrysanthemum
Chrysanthemum is often consumed as tea, but it can trigger severe allergic conjunctivitis. Individuals with a history of allergic conjunctivitis, particularly those who have experienced hay fever (hay fever), should exercise particular caution, as chrysanthemum consumption may easily induce allergic reactions in such individuals.
4. Chili Peppers
Chili peppers are rich in vitamins A and C. Extracts from them are sometimes formulated into eye drops to treat meibomian gland dysfunction and conjunctivitis. However, due to their irritating properties, they can exacerbate the irritation symptoms of conjunctivitis. There have been reports of corneal ulcers occurring in some patients after using eye drops made from high-concentration chili pepper extracts.
5. Citral
Citral is the primary component of lemon oil. Studies indicate that monkeys administered small doses of 2–5 mg citral experienced elevated intraocular pressure, with severe cases developing secondary glaucoma. Similar toxic side effects may occur in humans, necessitating caution during use.
Herbal medicines containing belladonna alkaloids can also cause elevated intraocular pressure and secondary angle-closure glaucoma. This is because they dilate the pupil, impairing aqueous humor drainage. Additionally, the commonly used Chinese herb ephedra may also elevate intraocular pressure.
6. Carrot-related herbs
While no specific studies link excessive carrot consumption to cataracts, some scholars suggest it may increase cataract risk. This is because carrots contain coumarin and psoralen, which can transform into toxic substances under ultraviolet light.Ultraviolet radiation itself can cause cataracts, and these toxic substances further increase the risk of cataract development.
With the wide variety of Chinese herbal medicines available, caution is warranted regarding potential adverse effects on the eyes. Should any ocular abnormalities arise—such as redness, itching, pain, photophobia, tearing, decreased vision, or flashes of light and dark spots—prompt medical evaluation and treatment are essential.