The use of mare's milk and the consumption of Plantago ovata, particularly in "alternative medicine", has become more widespread 

We present the case of a 55-year-old, former smoker, who sought medical attention for dispnea and wheezing related to the handling of lyophilised equine milk or activated charcoal at his workplace (where natural nutritional supplements are manufactured). The patient also reported intermittent perennial rhinitis. During follow-up, the patient experienced an episode of angioedema, acute dispnea and vomiting after consuming a Plantago ovata tablet. No other reactions to food were reported.

Spirometry revealed an FEV1/FVC ratio of 62.98%, FEV1 of 80% and a positive bronchodilator response of +17% (550 mL). Skin prick tests were positive for house dust mites and lipid transfer protein. Specific IgE testing showed sensitisation to house dust and cow's milk. An ALEX microarray test was requested, which showed positivity to mare’s milk (Equ c_milk 37.82 kUA/L) and camel milk (but not to other mammalian milks), negative for animal epithelia (included Equ c 1, 3, and 4); positive results for LTP from peach, subunit 11s globulins and sesame albumin. Prick-by-prick with lyophilised equine milk and Plantago ovata were positive and negative for activated charcoal.  A basophil activation test with equine milk was positive (96% stimulation). Immunoblot analysis identified IgE-binding proteins of 20 and 30 kDa in equine milk and 15 and 20 kDa in Plantago ovata. No bands were identified for the activated charcoal extract.

The patient was diagnosed with occupational asthma due to inhaled freeze-dried mare's milk allergy and anaphylaxis due to Plantago ovata

It has been reported that β-Lactoglobulin, α-lactalbumin, and κ-casein are the main allergens in mare's milk. The sensitisation pattern in our patient may correspond to β-lactoglobulin [18 kDa] and Casein (Equ c8) [23–36 kDa]. Furthermore, Equ c1, a lipocalin, is considered the main allergen in horse epithelium, and Equ c3, a serum albumin, shows cross-reactivity with serum albumins from other mammals. According to the current literature, no case of mare's milk allergy has been described.