What Are Symptoms of Mast Cell Activation Syndrome?

Mast cell activation syndrome (MCAS) can cause allergy symptoms. Learn about causes, diagnosis, and treatment

Mast cell activation syndrome (MCAS) can cause allergy symptoms that affect different body functions at the same time. Symptoms may include:

• Swelling
• Tingling
• Itching (pruritus)
• Rashes
• Irritation
• Vomiting
• Headache
• Dizziness
• Chronic pain
• Skin turning red (flushing)
• Diarrhea
• Constipation
• Rapid pulse (tachycardia)
• Low blood pressure (hypotension)
• Weakness
• Fainting (syncope)
• Sweats
• Stomachache

Some key signs of MCAS include:

• Symptoms in more than one organ
• Symptoms that go back and forth or keep  repeating
• Presence of various triggers
• Trouble sorting out specific triggers
• Quick changes in symptoms

What is mast cell activation syndrome?

MCAS is a condition that makes mast cells release an inappropriate amount of chemicals into the body, causing allergy symptoms or a variety of other symptoms. 

Mast cells are blood cells that help your immune system fight infections. When the Immunoglobulin E (IgE) antibody on mast cells comes into contact with an allergen, the mast cells release chemicals into the body, causing allergic reactions.

In healthy people, these released chemicals protect the body and help it heal. In someone with MCAS, however, it can trigger a negative reaction.

What causes mast cell activation syndrome?

It’s unclear what causes MCAS. It is called an idiopathic condition because it is not caused by any other disease or associated with a specific allergy or cause.

People who have this disorder may struggle to identify the specific thing that triggers the allergic responses, and may experience new triggers often.

How is mast cell activation syndrome diagnosed?

Getting a diagnosis of MCAS can be complicated and may require seeing various specialists. This can happen because many signs and symptoms may mimic other health conditions, and it's difficult to determine the exact reason they’re happening.

Your doctor will take a detailed medical history and perform a physical examination. They may order tests to look for tryptase, histamine, and prostaglandin levels. While there are no conclusive tests, your doctor may look for three specific things: 

1. Allergy indications and different side effects in at least two organs that continue to return or are chronic.
2. Higher than typical levels of tryptase, histamine, or prostaglandins in the body.
3. Improvement after medications that block chemical substances delivered by mast cells (anti-mediator treatment).

How is mast cell activation syndrome treated?

The treatment of mast cell activation syndrome is mainly focused on providing symptomatic relief.

Medications

Antihistamines and other medications that block these chemical mediators can help. These may include:

• First-gen H1 blockers
  • Diphenhydramine
  • Hydroxyzine
• Second-gen H1 blockers
  • Loratadine
  • Cetirizine
  • Fexofenadine
• H2 blockers
  • Ranitidine
  • Famotidine
• Ibuprofen
• Leukotriene inhibitors
  • Montelukast
  • Zafirlukast
• Corticosteroids
• Monoclonal antibodies
  • Omalizumab

Lifestyle modifications

Stress can trigger MCAS, and side effects from MCAS can trigger stress. This can lead to an endless cycle of allergic reactions. Thus, stress management is important in managing the condition. Ways to manage stress include:

• Talking with a therapist
• Connecting with your loved ones
• Getting enough rest and a eating healthy diet
• Using self-care strategies
• Staying active
• Spending time on hobbies