Food intolerance: how to spot the signs

Intolerance is not allergy

Food allergy involves the immune system and can cause severe reactions, such as swelling of the mouth and shortness of breath. Intolerance usually involves digestion: the body has trouble processing a component of the food and reacts with gas, bloating or diarrhea. The difference matters, because allergy requires immediate medical care.

Read also: Anxiety signs in the body: how to recognize them and Too much caffeine: signs you are overdoing it.

The most common example: lactose

According to NIDDK, a US health institute, symptoms of lactose intolerance usually appear 30 minutes to 2 hours after consuming milk or dairy: bloating, gas, diarrhea, nausea and abdominal pain. Many people who have trouble digesting lactose tolerate small amounts without symptoms.

A doctor can make the diagnosis based on history and, when needed, tests such as the hydrogen breath test.

Source: NIDDK, lactose intolerance.

How to observe without spending

The first step costs nothing: a food diary for two or three weeks. Write down what you ate, how much, the time and any symptom in the following hours. Patterns appear over time, and this record helps a lot at the appointment.

• Also note sleep, stress and medications, which affect the gut.
• Do not cut several foods on your own at the same time: it makes the cause harder to find and can unbalance your diet.
• Any prolonged exclusion should be done with guidance from a doctor or dietitian.

Other causes for the same symptoms

Bloating and diarrhea also appear in irritable bowel syndrome, celiac disease, infections and medication effects. That is why the diary is a starting point, not a conclusion. Also see hidden sugar in food.

Intolerance is not allergy, and that changes everything

The British health service explains the difference plainly: food intolerance does not involve the immune system, usually depends on the amount eaten, shows up hours later and, although it disrupts life a lot, does not cause a severe reaction. Food allergy involves the immune system, can appear with traces of the food and within minutes, and can be severe.

In the most common case, lactose intolerance, the US institute NIDDK explains that it happens because of insufficient production of the enzyme lactase, and that many people tolerate small amounts, especially alongside other foods.

Source: NHS, food intolerance.

Source: NIDDK, lactose intolerance.

Beware of the test that promises to list 200 foods

IgG food tests, sold as intolerance mapping, are discouraged by allergy organizations. The American Academy of Allergy, Asthma and Immunology states that the presence of IgG against a food indicates exposure to it, not disease, and that the test should not be used to diagnose allergy or intolerance.

The practical result of using this kind of test is usually an unnecessarily restricted and expensive diet.

Source: AAAAI, on the IgG food test.

The cheap and reliable path

What works without spending much is method, not testing:

1. Symptom diary for two to four weeks, noting what you ate, how much, the time and the symptom.
2. Elimination test with guidance, removing one food at a time for a set period.
3. Reintroduction, the part most people skip and the one that really confirms.
4. Professional evaluation before cutting whole food groups, especially in children, pregnant women and older adults.

Signs that call for quick medical evaluation: unexplained weight loss, blood in the stool, anemia, persistent vomiting and shortness of breath or swelling after eating.

When to seek help

Seek care if there is unexplained weight loss, blood in the stool, diarrhea that does not go away, strong pain, fever or repeated vomiting. Signs of allergy, such as swollen lips, hives or shortness of breath after eating, call for immediate care.