Symptoms appear soon after eating (minutes to hours) and are a wide range of different manifestations. There may be headaches, hives, red and itchy skin and  itchy eyes, runny nose, swelling, heart palpitations, migraines, hot flashes, asthma, diarrhea, cramps, muscles and joint pain, panic attacks, anxiety, IBS.

The less common are: gum inflammation, contact dermatitis , fibromyalgia, difficulty regulating body temperature, lactose and gluten intolerance, POTS, hives on chest, blurred vision, tinnitus, Tingling in hands, arms, chest, face, feet, sore throat and tongue, Psoriasis, allergic reaction to nickel, acid reflux, high blood pressure, blood pressure drops, constipation, paranoia, anger, sensitivity to light, ringing in the ears, acne

The first symptom that made me realise I might have a high histamine tolerance was an intense cough after eating pickles. My face turned red and my stomach became bloated. Other symptoms I experienced were insomnia, brain fog, depression, swelling (angioedema), vasodilation (increased blood flow), which can cause heavy periods, bronchitis (inflammation of the airways), frequent urination, increased hunger, water retention and, in the long term, hair loss, a swollen face and worse PMS.

Histamine is not only related to food. Things like poor sleep quality, stress, exhaustion, exercise, medication, overworking and changes in the environment or hormonal changes, can also exaggerate symptoms.