Why Am I Suddenly Allergic to Products I Never Reacted to Before?
poison ivy, are so strong that it only takes 2 exposures before this occurs). Once a person is sensitized, subsequent reactions to the allergen occur more quickly. Each time a person is re-exposed to the substance, the immune system responds faster and with more cells to trigger the inflammatory reaction. It may take days, weeks, months or years, but eventually the tolerance threshold is breached and visible/palpable/sensory symptoms appear – such as itching, redness, swelling, skin lesions (papules, vesicles). Symptoms may resolve shortly after all contact with the allergen is discontinued, or they may linger for up to a month. How sensitive a person is to developing allergic contact dermatitis depends on a few factors:You’ve used the same lip balm forever, and you never had a reaction to it before. But all of a sudden (it seems), you have itchy lips or a bit of a red rash around your mouth or even a few small, itchy bumps. If you really think about it, maybe you recall this happening a few times in the past, but the symptoms were no big deal and would go away on their own. Now the itching and redness is coming on faster after applying the lip balm and it lasts longer than it previously used to. Sound familiar? This is allergic contact dermatitis and while it appears to develop rather suddenly, that is not exactly the case. The inflammatory response that leads to these kinds of skin rashes is a complex series of events within your immune system that develops over time. In immunology (the branch of biology/medicine concerned with immune responses), the most commonly used classification system of immune reactions recognizes 4 types of hypersensitivity reactions. In allergic contact dermatitis, we are concerned with Type IV Hypersensitivity Reactions. Generally, these types of reactions are designed to protect your body from possible damage caused by microbial and foreign agents (virus, bacteria, foreign tissues). When your body is first exposed to the invader, you become sensitized – you develop a sensitivity to it, in the hope that your body will recognize the invader again in the future and will mount an immune attack against it before it causes harm to your tissues. But allergic contact dermatitis is a deviant form of these hypersensitivity reactions; it develops in a similar way, but instead of protecting your body from the allergen, the immune response actually causes damage to your skin. Type IV Hypersensitivity Reactions are cell-mediated immune responses – they require a series of interactions between various cells in the immune system in order to create sensitization in an individual. That means several steps need to be taken before a person becomes sensitive to a substance. Thus, these types of hypersensitivity reactions are sometimes referred to as “delayed hypersensitivity reactions.” Most allergens are relatively weak in eliciting a response from the immune system and it takes several instances of exposure before sensitization occurs (although some, like
- Poor genetics (some people have more genetic factors that make them susceptible to developing allergic contact dermatitis)
- Compromised skin barrier (seen in atopic patients, excessively dry skin, skin already compromised by dermatitis or ulcers)
- Fewer suppressor cells (cells in the immune system that actually increase a body’s tolerance to allergic substances)
- Increased frequency of re-exposure to the allergen
- The person’s level of sensitivity to the allergen
- The concentration of allergen absorbed by the skin
- Duration of exposure to the allergen
- Location of exposure to the allergen (a stronger response usually occurs at the original site of initial exposure)
Topics: Allergies, Eczema, Rashes
Publish Date: June 6, 2017 *Articles may include updates since original publishing.