Doctor: Does frequent exposure to onions cause blindness?

Recently, the public has been abuzz with the news that hundreds of people in the onion growing area have suffered vision loss, even blindness, due to long-term exposure to this agricultural product. Is there a medical basis for this?

There is no scientific evidence to suggest that red onions cause blindness.

On July 25th, Dr. Tang Hong Chau, Director of Saigon Cach Mang Thang Tam Eye Hospital, stated that there is currently no medical evidence to suggest that prolonged contact with red onions causes blindness or permanent corneal damage. However, continuous and unprotected contact may cause temporary irritation, such as burning, tearing, redness, and even mild conjunctivitis if proper hygiene is not maintained.

Medical literature has not recorded any cases of permanent corneal damage caused by red onions. However, there are some reports of allergic conjunctivitis and prolonged conjunctival irritation, but these usually resolve well after cessation of exposure or treatment.

Specialist Doctor Tang Hong Chau analyzes the eye structure using a model.

PHOTO: LE CAM

"The spiciness in red onions is due to the enzyme alliinase, which is released when the onion is cut or crushed. This enzyme produces propanethial-S-oxide – a volatile gaseous compound that irritates the lacrimal glands, causing tearing, stinging, and a burning sensation. If exposed multiple times a day, the eye mucosa may experience mild irritation, causing redness, fatigue, or prolonged discomfort," Dr. Chau explained.

Many cases of eye injury are due to the nature of the occupation.

In clinical practice, Dr. Chau said he has encountered many cases of patients with eye injuries related to their occupations, from welders and carpenters to farmers, due to exposure to dust, chemicals, or strong light without proper protection.

For those who grow or process shallots, the risk is similar if they don't wear glasses or work in poorly ventilated environments.

"Common risks if people grow shallots in unprotected conditions include irritant conjunctivitis , dry eyes , or even minor corneal abrasions due to rubbing the eyes vigorously when irritated. In the long term, if not properly cared for, it can increase the risk of infection or temporarily affect vision," Dr. Chau said.

The pungent taste in red onions comes from the enzyme alliinase, which is released when the onion is cut or crushed.

Photo: AI

How to prevent eye injuries when working in dusty or irritating environments.

"Exposure to shallots does not cause blindness if proper protection is taken. However, carelessness, lack of protection, and neglect of eye care can lead to prolonged irritation. Caring for the eyes not only helps protect vision but also maintains the health and productivity of shallot farmers – a valuable traditional occupation in many localities," shared Dr. Chau.

To prevent eye injuries, Dr. Chau advises workers to wear clear protective glasses while working to prevent dust and irritating fumes, rinse their eyes with saline solution after each day's work, avoid rubbing their eyes with dirty hands, especially after contact with onions; work in well-ventilated areas, or use an exhaust fan when peeling onions indoors. Use eye drops if you experience significant stinging and seek medical attention if you experience prolonged redness or pain in your eyes.

Can Tho leaders deny reports that many people growing purple onions have gone blind.

As reported by Thanh Nien newspaper, on July 23, the City Party Committee, People's Council, People's Committee, and Vietnam Fatherland Front Committee of Can Tho City organized a meeting with businesses and investors for 2025. Representatives from more than 100 businesses and investors operating in the area attended.

At the conference, Mr. Le Xuan Dac, General Director of Dac An Investment - Production - Business Company Limited (hereinafter referred to as Dac An Company), stated that Vinh Chau town in the former Soc Trang province has approximately 4,000-6,000 hectares of agricultural land; of which about 1,700 hectares are used for growing purple onions. According to Mr. Dac's research, among the thousands of farmers growing purple onions, about 1,200 people have gone blind due to the pungent chemicals in the onions damaging their corneas. Despite this, the people here still consider this a traditional occupation, passed down from father to son.

However, according to Mr. Ngo Thai Chan, Director of the Department of Agriculture and Environment of Can Tho City, the claim that growing purple onions leads to blindness is incorrect. About 20 years ago, farmers lacked proper methods for preserving purple onions and didn't know how to protect their health, which affected their eyesight. Currently, purple onion growers are not experiencing blindness on such a large scale as the Dac An Company reported.

Source: https://thanhnien.vn/bac-si-tiep-xuc-nhieu-voi-hanh-tim-co-gay-mu-loa-185250724232927928.htm