Histamine intolerance and eczema

Is there a link between histamine and eczema? If you look at histamine intolerance sites, they list eczema, or some form of skin rash as a possible symptom. Most eczema sites don't list histamine as a trigger. If you asked your dermatologist, they would probably say no. But if you look at the medical research literature, it suggests probably, but they haven't done enough studies

One case study of a 6 year old boy
It turns out that all those blogs citing a link between histamine and eczema really rely on one case study. In 2011, the Annal of Dermatology published a paper on the case report of a 6 year-old Korean boy who had eczema. It's a fairly easy to read paper, so I'll link it here, but the summary is below for those who don't want to read it.

Parents of this boy complained to doctors that their son's symptoms get worse after eating pork. To test this hypothesis, the doctors made sure the boy was normal and then gave him two challenges under observation. The boy started complaining 90 min after he was fed 200g of boiled pork. At 7 hours, they noticed more lesions, and by 9 hours later, his skin was oozing in parts. They then treated his eczema and tested him with 60g of pork two days later. This time, his eczema did not react.

The doctors noted that the boy's diet was full of fruits and vegetables such as oranges and spinach, and fish like mackerel. He also tended to consume one type of food in large quantities. After teaching his parents to feed him a low histamine diet, by avoiding a list of high histamine foods, the boy's eczema was much improved. They stopped medications after 1 month on the diet, and the boy showed no signs of eczema 7 months later.

There is one issue that is unclear to me, which is what else they fed him on the first day of the pork challenge. They mentioned feeding him kimchi, beef boiled in soy sauce, and rice, the two former foods potentially have a high histamine content. It was not made clear whether they fed him those same foods during the 60g pork challenge. But given that the boy completely recovered on a low histamine diet, it is certain that his eczema is primarily due to the histamine in his diet.

Beyond the Korean case study
The reason I like the Korean case study is because they were able to cleanly test the hypothesis and prove that eliminating dietary histamine can cure eczema. There are some previous studies that show a correlation between histamine and eczema but they have limitations. I have reproduced the abstracts, but some of the papers are too old to be found online.

1. Some eczema patients have higher levels of histamine in their blood (1983 study)
Abstract:
Plasma histamine concentrations were determined using a radio-enzymatic assay in fifty-four patients suffering from atopic eczema and in thirty-nine controls (contact dermatitis, psoriasis and normal non-atopic healthy volunteers). While in none of the controls histamine levels in plasma exceeded 1 ng/ml, seventeen out of fifty-four patients with atopic eczema showed increased plasma histamine concentrations ranging between 1.2 and 5.2 ng/ml. Elevated plasma histamine levels were found mostly in patients with severe eczema and high serum IgE levels. Longitudinal studies in seven patients revealed normal plasma histamine values during clinical remission.

I find it interesting that they compared atopic eczema patients with contact dermatitis and psoriasis patients. Only 17/54 (30%) eczema patients had above normal levels of histamine. Of the patients with abnormal histamine levels, they noted that their eczema improved coincided with low levels of blood histamine. The question, however, is where is the histamine coming from?

2.  Food histamine increases blood histamine levels in a sub-set of eczema patients (1989 study)

 Abstract:

Thirty-three patients with atopic dermatitis underwent double-blind placebo-controlled food challenges for evaluation of the role of histamine in hypersensitivity to food. After suspect foods were eliminated for 10 days, oral challenges were performed with up to 8 g of dehydrated food. A total of 35 positive challenges elicited symptoms that were cutaneous (31), gastrointestinal (17), nasal (8), and respiratory (6) within 10 to 90 minutes. Forty-one food challenges were negative, and all 60 placebo challenges were negative. Only the group of patients with positive food challenges had a significant mean (±S.E.M.) rise in the plasma histamine concentration, from 296±80 pg per milliliter before challenge to 1055±356 after challenge (P<0.001). Rises in plasma histamine that were seen after these positive oral food challenges implicate mast-cell or basophil mediators in the pathogenesis of food allergy, including cutaneous changes in patients with atopic dermatitis.

 

 This answers our previous question of where the histamine is coming from. Note that only the group of patients who reacted to the foods tripled their blood histamine concentration. Symptoms could be seen 10-90 minutes after the food was ingested, and all 60 placebos were negative. And unlike the general population that have headaches or nasal symptoms of histamine intolerance, 31/35 of these positive challenges resulted in skin related symptoms.

3. 30% of eczema patients may be histamine intolerant (2009 study)

This study isn't particularly well done (seeing that they did not put everyone on the same diet), but I will report the results since the information can still be salvaged.

 

They gathered 58 patients and put them on a low histamine diet for 1 week. They noted that 12 of 36 of them improved (some dropped out because they couldn't keep to the diet) after one week, and this same group of people reacted badly twice to histamine given in a pill. The other 24 patients who did not improve during the first week also did not do worse when given histamine in a pill.

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These are the 4 relevant studies that I know of. If you want me to look at any other studies, pass me the link. But as far as I know, these are the only 4 papers. I think the studies definitely point to something interesting, but there has been no larger follow up, which is a great pity. If it is true that 30% of eczema patients can improve their lives by adhering to a low histamine diet, we should really be trying it out at home.