Medically reviewed by Marla Anderson, MD
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Indolent systemic mastocytosis (ISM) symptoms appear when mast cells release chemicals such as histamine and tryptase. Symptoms include flushing, itching, hives, stomach pain, diarrhea, brain fog, bone pain, and sometimes severe allergic reactions like anaphylaxis. For most people, symptoms are triggered by specific factors. Here are 10 of the most common triggers that can lead to ISM symptoms.
1. Insect Stings
Stings from insects such as bees, wasps, ants, and flies are common triggers. They can also be potentially dangerous triggers, with stings possibly leading to anaphylaxis. Venom allergy testing can help identify people at risk for severe reactions. For people with ISM and a confirmed venom allergy, venom immunotherapy may help lower the risk of future anaphylactic reactions.
2. Temperature Changes
Temperature changes—especially extreme hot or cold—can trigger ISM symptoms. Changes in temperature can activate mast cells, thereby leading to symptoms. Healthcare providers often recommend that people with this trigger avoid extreme temperature changes.
3. Skin Trauma
Mild rubbing or pressure on the skin can cause friction and minor trauma, two known triggers for mast cell activation. This is also linked to a change known as Darier’s sign, which is a common finding in mastocytosis, where rubbing a skin lesion causes redness or swelling. Things like tight clothing, vigorous towel drying, harsh scrubbing, or skin scratching may trigger symptoms.
4. Alcohol
Alcohol is a common trigger for mast cell activation in people with ISM. Alcohol causes the release of chemicals from mast cells, leading to ISM symptoms. Because of this connection, people with ISM are often advised to avoid alcohol.
5. Spicy or High-Histamine Foods
Dietary triggers can vary from one person to another.
Spicy foods are a common trigger in ISM. Certain spicy foods can trigger symptoms such as flushing, stomach pain, diarrhea, or other digestive issues.
High-histamine foods, such as fermented products, aged cheeses, and cured meats, may also lead to ISM symptoms.
6. Medications
Several commonly used medications can trigger mast cell activation in people with ISM. These may include:
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Opioids
- Certain antibiotics
- Anesthetics
- Contrast dyes used in imaging tests
- Some muscle relaxants
Since reactions can be serious, providers recommend people with ISM keep a list of medications they should avoid. They may also prescribe preventive medications such as antihistamines or steroids before surgery, medical procedures, or imaging tests with contrast dye to reduce the risk of a reaction.
7. Stress
Stress is not just psychological; it can cause physical effects on mast cells. Stress and anxiety can activate mast cells and trigger symptoms in people with ISM.
Many people with ISM also experience symptoms like anxiety, depression, or mood changes. This can create a cycle where stress worsens physical symptoms and, in turn, the symptoms increase stress and anxiety.
8. Strenuous Exercise
Intense physical activity is another common trigger for people with ISM. People with ISM may be advised to avoid or modify strenuous exercise since it can activate mast cells and worsen symptoms. However, that does not mean people with ISM should avoid exercise completely; gentle exercise is often well tolerated.
9. Surgery
Surgery and medical procedures can be a trigger for many people with ISM. This is why providers may recommend preventive medications before surgery, imaging tests with contrast dye, or even minor procedures. Endoscopy in particular may be a trigger.
10. Vaccines
Vaccines can sometimes trigger mast cell activation in people with ISM. That doesn't mean people with ISM should avoid vaccinations; most vaccines are generally well tolerated, and the benefits of protection usually outweigh the risks. However, people must be monitored after vaccination and should have access to epinephrine in case of a severe allergic reaction.
Avoiding Your Triggers
Identifying and avoiding your triggers is one of the most important parts of managing ISM. Keep a symptoms log to track what environmental, physical, or dietary factors may be triggering your symptoms. If you notice you have a consistent trigger, try your best to avoid it.
Sometimes triggers are unavoidable or unknown. Since people with ISM have a higher risk of anaphylaxis when exposed to a trigger, you should carry self-injectable epinephrine at all times.
