Grasses can already become a cause of discomforting symptoms for allergy sufferers at the end of April. Grass pollen is followed by weed pollen, such as mugwort, at the beginning of the summer months. The grass and weed pollen season does not end until late September/early October [1]. Therefore, it can often be difficult to identify the true cause of allergy during this period. Allergy to grasses and weeds – what should we know about it?
Grass and weed allergy – what symptoms do they cause?
Symptoms that people who are allergic to grass and weed pollen may experience include:
- itching,
- sneezing,
- blocked, runny nose,
- red, burning and watery eyes.
In some cases, people with a mugwort allergy may develop symptoms of the so-called oral allergy syndrome (Oral Allergy Syndrome, OAS) and sometimes even anaphylaxis after eating certain foods as a result of cross-reactions. To identify which pollens are responsible for allergy symptoms, laboratory tests can be conducted. More specifically, this involves determining whether there are IgE antibodies against specific pollens in our blood. There is no need for special preparations for such tests. These tests can be carried out at any time of day. Fasting is not necessary, and there’s no need to discontinue any medications, even antiallergy ones. A small amount of blood is required for the tests. Antibodies can be measured against entire allergens (known as extracts). Recently, it has even become possible to analyse individual proteins (molecules) that make up a particular pollen. This form of diagnosis, known as molecular allergy diagnostics, enhances the sensitivity of serological tests. It not only allows for precise identification of which pollens are responsible for allergy symptoms, but also provides insight into whether immunotherapy can be effective and whether we can expect cross-reactivity, for example, with foods.
Grass proteins
The most important proteins of the grasses, specifically its main representative timothy (Phleum pratense), include Phl p 1 and Phl p 5 [2].
- Timothy amongst grasses
Phl p 1 and Phl p 5 are the main allergens of Timothy grass. This means that IgE antibodies in the blood serum against each of these proteins have been found in at least 50% of individuals with Timothy grass allergy. Antibodies against these two grass proteins serve as markers for primary allergy. Detecting the presence of antibodies against Phl p 1 and/or Phl p 2 allows for the diagnosis of grass allergy. These are also the two most important grass proteins when it comes to qualifying for immunotherapy. Detecting their presence indicates a potential for successful desensitization. Therefore, the absence of IgE antibodies against these proteins in grass-allergic individuals may be associated with the lack of effectiveness in desensitization [3].
It’s worth checking if the patient has antibodies against Phl p 7 or Phl p 12. The Timothy grass protein Phl p 7 belongs to the polcalcin family, while Phl p 12 belongs to the profilin family. Proteins from these two groups are widely present in the plant world. As a result, they might be responsible for positive results with other pollens. This is referred to as high cross-reactivity.
Profilins, unlike polcalcins, can be responsible for cross-reactions with fruits and vegetables. However, an important characteristic of profilins is their thermolability, which means that subjecting them to heat treatment diminishes their ability to trigger an allergic response.
Weed allergens
Examples of mugwort (Artemisia vulgaris) allergens include Art v 1 and Art v 3 [2].
- Mugwort among the weeds
Allergens from the profilin and polcalcin groups are also found in mugwort. This means that when conducting diagnostic tests based on whole allergens, known as extracts, we won’t be able to distinguish the primary cause of the allergy. In other words, in cases of sensitization to profilins and polcalcins, we can obtain positive results for grasses, weeds, and other plants. Even though the person isn’t actually allergic to those specific sources of allergens. Only by identifying additional molecules from mugwort can we differentiate whether the positive results are attributed to grass or weed proteins. It’s also possible that a patient might have both main grass and weed molecules present. In such cases, we can diagnose an allergy to plants from both groups. However, if positive results are only for profilins and polcalcins, either for one type of protein or the other, a diagnosis of allergy to those proteins cannot be made for that individual.
The main allergen that distinguishes these allergies and is necessary for diagnosing mugwort allergy is Art v 1. It is responsible for allergy even in up to 70% of individuals sensitive to this weed [4]. Detecting IgE antibodies in the serum against Art v 1 indicates a potential for effective immunotherapy, while their absence might lead to immunotherapy not producing the expected results. In sensitized individuals, it can cause allergic rhinitis and/or conjunctivitis, as well as asthma.
Allergies to grasses and weeds – be aware of cross reactions
A very similar protein to Art v 1 is found in sunflower seeds. Because of this, some individuals may experience symptoms of itching, swelling of the lips, tongue, or what is known as oral allergy, as well as angioedema and anaphylaxis after consuming it. This is why Art v 1 is an important protein in diagnosing ragweed allergy. Another protein found in ragweed that can cause similar symptoms after consuming foods containing similar proteins is the molecule Art v 3. This protein belongs to the nsLTP (non-specific lipid transfer protein) group, which includes proteins from peaches, apples, mangoes, peanuts, hazelnuts, walnuts, onions, and grapes [5]. It is thermostable, meaning that even after heat treatment, it can still cause severe allergic reactions.
Have you got the results? Make sure you show them to your doctor
The above-mentioned proteins are those most important to meadow thyme and mugwort. Their determination provides a lot of valuable information in the context of deciding which allergen to use for immunotherapy and the prognosis of its effectiveness. It also allows us to verify whether cross-reactions are possible, as well as predict the possibility of symptoms. Such a diagnosis allows us to obtain an individual allergy profile and formulate an appropriate diet if food elimination is necessary. Interpretation of the results requires knowledge of the individual proteins and their characteristics, which is why the results of molecular allergy diagnostics should always be interpreted by an allergologist. Therefore, if you decide to carry out such a test, do not look for help on the Internet on various support groups, and do not interpret it on your own, as such advice can have a significant impact on your symptoms. The allergologist will compare your symptoms with the results of the test and prescribe appropriate medical treatment if necessary.
______________
translation: Julia Majsiak
