MCAS symptoms MCAS (Mast Cell Activation Syndrome) symptoms may include:
Anaphylaxis or near-anaphylaxis
Flushing or redness of skin
Abdominal pain, nausea, vomiting, diarrhea
Headaches, migraines
Fatigue, weakness
Muscle and joint pain
Tachycardia, palpitations
Lightheadedness, fainting
Breathing difficulties
Skin itching, hives, rashes
Depression, anxiety, irritability.