Hidden Allergens
in Thai Food

Why Thai food is unusually high-risk for hidden allergens

Thai cuisine is built on layered flavors that originate in sauces and pastes added during cooking. Fish sauce functions as salt. Shrimp paste is part of the base for curry pastes. Peanut oil is a common cooking fat. None of these appear on a menu description, and Thai kitchen staff often don't think of them as "ingredients to mention": they're as fundamental as salt and oil in a Western kitchen.

The result: a dish described as "mixed vegetables with tofu" can be stir-fried in peanut oil, seasoned with fish sauce, and served with a shrimp paste-based dipping sauce. None of that is visible from the description, and the server may not know to flag it.

This guide covers where each allergen hides and how to flag it in Thai. If you want broader guidance on communicating at restaurants and which dishes to avoid, the Thailand Food Allergy Survival Guide is the main reference. For peanuts specifically — including oil types, curry paste risk, and dish-by-dish breakdown — see Hidden Peanut Ingredients in Thai Street Food.

Fish sauce: น้ำปลา (nam pla)

The single most common hidden allergen in Thai food. Fish sauce is used where salt would be used in Western cooking. It seasons dishes during cooking and is often added at the table as a condiment.

It appears in: pad thai, fried rice, tom yum soup, most Thai curries, papaya salad, stir-fried vegetables, and almost any dipping sauce. Even dishes at restaurants marketing themselves as vegetarian or "healthy" will typically use fish sauce unless the establishment specifically caters to strict vegetarians.

Thai to show: ไม่ใส่น้ำปลา · mai sai nam pla (no fish sauce)

Shrimp paste: กะปิ (kapi)

A strongly fermented paste made from ground shrimp and salt. It has a pungent, concentrated flavor and appears as a core ingredient in most curry pastes (green, red, panang), in the chili-based dips called nam prik, and as the base dressing in some versions of som tam.

Unlike fish sauce, shrimp paste is cooked into the dish at the paste stage: meaning it cannot be removed on request. Anyone with a shellfish allergy should be aware that ordering a curry prepared with a standard paste means consuming shrimp paste unless a specifically prepared alternative is available.

Thai to show: ไม่ใส่กะปิ · mai sai kapi (no shrimp paste)

Peanuts and peanut oil: ถั่วลิสง (thua lisong)

Peanuts appear in Thai cooking in two distinct ways: as a cooking fat (peanut oil in the wok) and as a visible garnish. Street food stalls typically cook in peanut oil as a matter of course. Whole or crushed peanuts are a standard topping on pad thai, certain noodle soups, and satay accompaniments.

The garnish issue is particularly relevant for cross-contamination: in a busy street food stall, peanuts are handled continuously, and the same utensils and surfaces are used across multiple dishes.

Thai to show: แพ้ถั่วลิสง · pae thua lisong (allergic to peanuts)

Dried shrimp: กุ้งแห้ง (kung haeng)

Small whole or chopped dried shrimp used as a flavor component. They appear in som tam as a standard ingredient, in fried rice, in stir-fried vegetables, and scattered through various noodle dishes. They can be ground finely enough that they're not visible in the finished dish.

This is one of the most commonly overlooked allergens for people with shellfish allergies traveling in Thailand. The volume of shrimp in each portion is small but sufficient to trigger a reaction in sensitive individuals.

Thai to show: ไม่ใส่กุ้งแห้ง · mai sai kung haeng (no dried shrimp)

Oyster sauce: ซอสหอยนางรม (sot hoi nang rom)

Less discussed than fish sauce but equally widespread. Oyster sauce is the standard finishing sauce in Chinese-influenced Thai stir-fries, including morning glory (pak boong), broccoli, and many noodle dishes. Like fish sauce, it's added during cooking and doesn't appear on most menus.

Thai to show: ไม่ใส่ซอสหอยนางรม · mai sai sot hoi nang rom (no oyster sauce)

Where each allergen appears