If you’ve been diagnosed with systemic mastocytosis (SM), you may have heard you should be careful with aspirin, or even to avoid it altogether. But is a bottle of pills found in most homes really that dangerous?
The answer is sometimes yes — and sometimes no. Learn why aspirin safety and SM is far from straightforward.
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How does aspirin work?
Aspirin (acetylsalicylic acid) is one of the oldest and most widely used medicines for pain, fever and inflammation.
Aspirin belongs to a group of medicines called nonsteroidal anti-inflammatory drugs (NSAIDs). This group also includes painkillers like ibuprofen (sold as Advil and Motrin, among other brands) and naproxen (Aleve). NSAIDs work by blocking cyclooxygenase (COX) enzymes, which are involved in the production of prostaglandins, chemical messengers involved in pain, inflammation and blood flow. Blocking COX enzymes means fewer prostaglandins reach the brain, and you feel less pain.
Most NSAIDs block COX enzymes only temporarily. Aspirin switches them off permanently, so this effect lasts until your body makes new enzymes, which can take days.
Why aspirin can cause harm in systemic mastocytosis
In SM, the body has way too many mast cells, and they release their contents too easily. Research suggests that a specific type of prostaglandin, prostaglandin E2 (PGE2), acts as a natural brake on mast cells and helps keep them stable.
Aspirin releases that brake. By blocking COX enzymes, aspirin and other NSAIDs reduce production of PGE2. At the same time, the body shifts toward making more leukotrienes, which are chemical messengers that drive inflammation. With the brake weakened and leukotrienes rising, mast cells can more easily tip into activation.
In some people, this can trigger:
- Flushing, itching, or hives.
- Swelling.
- Breathing problems.
- Anaphylaxis, a severe allergic reaction, in rare cases.
But aspirin can help in SM, too
Since aspirin lowers prostaglandins across the board, its overall effect is not a simple “black or white.”
Prostaglandins are a broad group of chemical messengers with varied, sometimes opposing, roles. While PGE2 helps keep mast cells in check, other types can contribute to SM symptoms. One of these is the mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. mediator prostaglandin D2 (PGD2).
Read more: What people with mastocytosis should know about mast cell mediators
Mast cells are the main source of PGD2. Excessive production of PGD2 due to mast cell activationMast cell activation Describes when mast cells release histamine and other mediators into the blood stream in response to an allergen or other trigger. This leads to symptoms like fatigue, rash and, in severe cases, anaphylaxis. can cause SM symptoms like flushing, headaches, dizziness, low blood pressure and digestive upset.
Research suggests relatively low doses of aspirin are often enough to bring PGD2 back to normal, which may help ease these symptoms. That doesn’t mean you should start taking an aspirin every day to try and control symptoms, though — remember, aspirin can also cause harm in SM.
Should you avoid aspirin routinely?
Not necessarily. Although people with mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults. are more likely to react to NSAIDs, research suggests the risk is only somewhat higher than in the general population, and most reactions affect only the skin. If you have taken aspirin or other NSAIDs without problems since your diagnosis, you can usually keep using them. Allergy experts note that avoiding them across the board may be unnecessary, and that the decision is best made case by case.
Aspirin is something to talk to your doctor about. Your doctor will consider:
- Previous reactions. If you have reacted to an NSAID before, your doctor may advise you to avoid it. If you need aspirin anyway, your doctor may suggest a supervised test dose or desensitization, which means gradually introducing the drug under medical care.
- Your symptoms and test results. Aspirin treatment is usually considered when flushing or other symptoms persist despite antihistamines. This is especially true if a urine test shows high levels of a PGD2 breakdown product.
Aspirin is not off-limits for everyone with SM, but it isn’t a casual choice either. Beyond mastocytosis, your doctor will also consider your other health conditions and medicines before deciding whether aspirin is for you.
