Overview

Have you ever lifted a glass at a restaurant, excited for a drink, only to notice a faint “rotten egg” smell? It can instantly ruin the moment. Recently, restaurateur Kabir Chugh pointed out on Instagram that this unpleasant odour may occur when restaurants wash glasses and immediately store them upside down, trapping stale air inside. But is “trapped air” really the problem? Experts say the issue goes beyond that.

Moisture, Not Just Air

Chetan Raj, Executive Sous Chef at The Claridges, explains that improper storage may contribute to the problem, but stale air alone does not cause the smell. The real culprit is moisture. If glasses are not rinsed thoroughly, remain wet inside, or are stored upside down on a flat surface without proper airflow, moisture can stay trapped inside. In such damp conditions—especially when racks or storage surfaces are not clean—bacteria can grow rapidly. Some of these bacteria release sulphur compounds, which produce the distinctive rotten egg smell. In simple terms, the odour usually results from moisture retention, inadequate drying, and bacterial growth, rather than air trapped inside the glass.

Other Reasons a Glass May Smell

Drying issues are not the only cause. Several other factors can also lead to unpleasant odours in glasses, including:

• Dirty or poorly maintained dishwashers
• Detergent residue left after washing
• Poor-quality or contaminated water
• Incorrect washing temperatures
• Hard water deposits react with organic matter
• Improper storage and handling practices

Dr Garima Tiwari, Head of Clinical Nutrition and Dietetics at ShardaCare–Healthcity, Greater Noida, explains that moisture can stagnate inside glasses when they are washed and stored without adequate air circulation, particularly when they are kept upside down. Such damp conditions can eventually lead to foul, sulphur-like odours.

A Sign of Poor Hygiene

From a hygiene perspective, stagnant moisture is a warning sign. Dr Tiwari notes that damp environments encourage bacterial growth, while poor ventilation prevents glasses from drying properly. Wiping glasses with unclean cloths can also transfer odours and microbes. In busy restaurants, rushed cleaning cycles or poorly sanitised equipment may further increase the risk of biofilm formation—a thin layer of bacteria that clings to surfaces and can produce unpleasant smells.

Is It Safe to Drink From Such Glasses?

Ideally, no. A smelly glass may not always cause immediate illness, but it often indicates gaps in basic hygiene practices. “A foul smell may indicate shortcomings in food safety protocols,” Dr Tiwari cautions. Possible risks include exposure to harmful bacteria, cross-contamination with other utensils, and the presence of mould or bacterial spores in damp conditions. If a glass smells unpleasant, it is perfectly reasonable to ask the restaurant for a replacement.

Source: The Indian Express