Symptoms and causes

Symptoms and causes

Excess histamine exposure can lead to a variety of symptoms, including:

  • Neurological: Headaches, dizziness, nausea, sleep problems, symptoms resembling panic attack, fatigue, confusion.
  • Gut: Abdominal cramps, diarrhea, heartburn.
  • Skin: Itching, hives, swelling, flushing, rash, eczema, acne.
  • Respiratory: Nasal obstruction, sneezing, runny nose, seasonal allergies, asthma.
  • Eyes: Irritation, redness, watery eyes.
  • Circulatory: Drop in blood pressure.
  • Tissue swelling, especially on the face, mouth, and throat.
  • Irregular periods.

The symptoms can last anywhere from a few hours to a day.

Other signs of histamine intolerance for women:

  • Women with histamine intolerance often improve dramatically during pregnancy. The placenta secretes massive amounts of DAO that reduces histamine levels while a woman is pregnant. However, problems often return after birth.
  • Menstrual pain, headaches, and hives. Estrogen stimulates the release of histamine and inhibits DAO, which aggravates histamine intolerance symptoms during stages of the menstrual cycle when estrogen levels increase (usually mid-cycle and during ovulation). Histamine levels have been shown to peak around mid-cycle in women. Histamine can also stimulate the release of estrogens.


As mentioned earlier, histamine intolerance is in most cases caused by problems in the DAO enzyme. Common causes include:

  • Gut problems: People with gut problems often have low DAO activity in the gut, which results in excess histamine exposure. DAO is found in large quantities in the small intestine villi (the small hair-like projections in the small intestine), and damage or problems in the small intestine can reduce DAO activity and lead to histamine intolerance. Animal studies have shown a dramatic reduction in DAO following small intestine damage, which explains why people with gut problems are at higher risk of histamine intolerance. This also means that you should first fix any gut problems you may have before tackling histamine intolerance.
  • Bacterial dysbiosis: Certain gut bacteria produce histamine from undigested food. This is one reason why some people suddenly get acne after taking antibiotics. The antibiotics changed the gut flora in a way that boosted histamine-producing micro-organisms.
  • Vitamin B6 deficiency: DAO requires vitamin B6 to function properly, so a shortage of B6 significantly inhibits DAO activity and increase histamine levels.
  • Certain drugs can also release histamine or inhibit DAO. If you suspect histamine intolerance and take medications regularly, check with your doctor whether the drugs you have are problematic for histamine intolerance.
  • High histamine levels. High histamine levels have been shown to inhibit DAO, which means histamine intolerance creates a cycle the perpetuates itself. However, a treatment that significantly reduces histamine levels (such as low histamine diet, but not antihistamines that simply block histamine) can break the cycle and restore normal DAO activity.
  • Chronic stress. Stress hormones trigger the release of histamine, and stress can compromise the intestinal barrier, which allows more histamine to leak from the gut.

About Me

Hi, I am Acne Einstein(a.k.a. Seppo Puusa). I'm a bit of a science nerd who is also passionate about health. I enjoy digging through medical journals for acne treatment gems I can share here. You can read more about my journey through acne and how I eventually ended up creating this.