We recently began offering IgE testing here at NeuroScience, Inc., and just about the same time an interesting, but disturbing study about allergies hit the newswire. It appears, based on a survey of nearly 38,000 children, that the prevalence of childhood allergies is about 1 in 12, or twice what we previously thought (you can read additional commentary in this article in the Huffington Post). The underlying causes remain unclear, but the health effects of allergies can, of course, be quite serious. We’ll discuss this interesting study in a future post.
While I think we’re all fairly aware of the situation of food allergies in kids, I’m surprised by how often I hear healthcare providers tell me that they don’t feel the need to test their adult patients for allergies to foods and inhalants such as pollens and pet dander, because most of their patients have already had skin prick testing done previously in their lives.
On the contrary, there are several reasons why it is important to test for IgE allergies more than once and in some cases frequently throughout life. For example, our gastric acid levels can fluctuate over the years. Low gastric acid has been found to be a causative mechanism in the induction of IgE-mediated allergy (Pali-Schöll 2010; Riemer 2010). The stomach uses pepsin, a gastric protease, to partially destroy dietary proteins, a process essential for oral tolerance to foods. Low gastric acid levels can occur due to regular usage of antacids and proton pump inhibitors (e.g. Prilosec, Prevacid, and Zegerid), or inherently low gastric acid production (aka hypochlorhydria).
In addition, a patient’s sensitivity to foods and inhalants can change over time, leading to worsening or alteration of symptoms (Kewalramani 2010). This progressive change has been coined the “allergic march” or “atopic march”, which has been well-documented in the progression of atopic dermatitis to allergic rhinitis and asthma (Zheng 2011).
How can we best determine whether a patient has Type I (IgE-mediated) hypersensitivities? Skin prick testing (SPT) has been used by allergists for years as the primary allergy diagnostic approach. While certainly a valuable tool in the allergy testing armamentarium, it may not identify all IgE allergies and therefore may provide an incomplete picture of a patient’s allergies. In addition, SPT does not evaluate Type III delayed-type (IgG-mediated) hypersensitivities, and is unable to quantify sensitization in patients (Kamdar 2010; ACAAI 2006).
In contrast, specific IgE serum testing is accurate, highly specific, and provides quantifiable measurements of Type I hypersensitivity (Eigenmann 2009; Jung 2010; Sampson 2001). Quantifiable IgE test results enable healthcare practitioners to identify allergy sensitization prior to major symptom eruption and to evaluate therapeutic interventions.
In conclusion, it’s a good practice to test, and re-test, patients for IgE allergies if they have reduced stomach acid, have allergic symptoms, suffer from intestinal hyper-permeability, or have only been tested using SPT.