Food allergies cause many reactions to those afflicted by one. Anaphylaxis occurs when you eat food that you are allergic to and the immune system to overreact by releasing too many chemicals at once causing the airways to swell. This is a life-threatening scenario that needs to be addressed by a medical professional immediately. Many patients with severe food allergies also carry an Epipen. If you are lucky, a food allergy will cause mild symptoms, such as breaking out in hives and mild coughing.

Here are four of the most common allergic reaction triggers that affect millions of people:

1. Milk

Tons of people are allergic to cow’s milk when they are born. At least there is a good chance that they will lose their milk allergy as they get a bit older. For those who don’t outgrow the condition, it can lead to some serious trouble. All dairy products must be avoided even if they only contain trace amounts of milk. This severely limits the number of foods that people with a milk allergy can stomach. Milk allergies and lactose intolerance often get mixed up. Lactose intolerance is different because it is a condition where the body doesn’t produce enough lactase to break down any lactose that is consumed.

2. Eggs

Being allergic to eggs is becoming more common as the years go on. Many kids grow out of their egg allergy as they become adults. The allergy triggers a few minutes after an egg is consumed. It can make the person vomit or give them a sizable rash. The symptoms can range from mild to life-threatening in extreme cases. The good news is that foods with eggs in them are easy to spot and avoid when necessary.

3. Nuts

Nuts are by far the most common triggers for allergic reactions. This is primarily because a nut allergy can be caused by a long list of other foods that may contain peanuts due to being manufactured in the same location. No matter how factories are set up, there is no way to fully prevent peanut residue from occasionally mixing into other products. Peanut allergies go hand in hand with asthma. Most allergic reactions caused by peanuts will also trigger an asthma attack. If a child is born with a peanut allergy, it is most likely that they will develop asthma pretty early on as well.

4. Shellfish

Shellfish is the third most common type of allergic reaction after peanuts and milk. A shellfish allergy can form in both kids and adults at any time in their lives. Those affected also need to avoid crayfish, shrimp, lobster, and crabs at all costs. Mussels, oysters, and clams all have a chance to produce a reaction as well. You can consult your doctor beforehand to see if you can eat them. That said, the best way to be completely safe is to eliminate them from your diet altogether.