When Your Allergy Medicine Doesn't Work Anymore

When an allergy medication doesn't work anymore—either as well as before or at all—it could be because your body is no longer reacting to the drug in the same way it once did or is clearing it too quickly for it to be effective. This is known as a drug tolerance.

This can happen after months and years of use. People who have chronic allergy symptoms are more likely to find that their allergy medicine stops working at some point.

It's also possible that an allergy medication is no longer working for you because your allergies have simply worsened and you need to change your treatment plan.

This article discusses how common allergy medications work, why they may stop working over time, what medications are most problematic in this regard, and what to do when you are no longer getting the relief you need.

Allergy Drug Tolerance

When an allergy medicine stops working, some people think the body has developed a natural defense (immunity) to it. Others may think they have become drug-resistant, as is possible with antibiotics that no longer work because bacteria has mutated.

Neither of these explanations is correct.

Instead, an allergy medication can stop being effective because the body has developed a tolerance to the drug—especially if it has been overused. This means the body has become more desensitized, or "used to," to the drug's effects.

There are two major reasons why drug tolerance happens:

• Dynamic tolerance is when a cell becomes less responsive to a drug the longer it is exposed to it. In some ways, it is similar to how the taste receptors on your tongue adapt to extra-spicy foods if exposed to them repeatedly.
• Kinetic tolerance is when the body responds to the ongoing presence of a drug and begins to break it down and excrete it more actively, lowering the drug concentration.

Sometimes, increasing the dose of the drug can make it work again. However, the effect is usually short-lived. And in the case of certain nasal sprays, doing this may actually make congestion worse—a phenomenon known as rebound congestion. (This can also occur if you take a lower dose for too long.)

If You're Tolerant of One Allergy Medicine Are You Tolerant to All?

Thankfully, being tolerant of one type of allergy medication doesn't mean all options for treating your symptoms are off the table. This is because the various classes of drugs that can be part of a treatment plan work in different ways:

• Antihistamines prevent histamine—the chemical the immune system floods the body with when it overreacts to an allergen—from attaching to cells of the skin, gastrointestinal tract, and respiratory tract. (The main function of histamine is to trigger inflammation.)
• Corticosteroids lessen the immune response and reduce inflammation, either locally with topical ointments or sprays, or systemically with oral or injected medications.
• Beta-agonists are commonly used in asthma inhalers to relax constricted airways in the lungs.
• Anticholinergics, also used in inhalers, block a neurotransmitter called acetylcholine, which reduces airway spasms and constriction.
  

Bronchodilators and Corticosteroids

You're more likely to develop tolerance to some allergy medications than others. For example, the risk of tolerance can be high with beta-agonists.

With this class of inhaled medication, tolerance is dynamic and linked to prolonged use or overuse of long-acting beta-agonists (LABAs) like Serevent (salmeterol).

Tolerance is more likely when the drugs are used on their own. In this case, it can have a "knock-on effect," inducing tolerance to the short-acting beta-agonists (SABAs) used in rescue inhalers.

This does not seem to happen with anticholinergic inhalants like Spiriva Respimat (tiotropium bromide) or glycopyrronium bromide, for which there is little risk of tolerance.

Dynamic tolerance can also happen with certain corticosteroid formulations, particularly topical ointments, and nasal sprays. Frequent, repeated use can rapidly desensitize the skin and mucosal tissues to the vessel-shrinking (vasoconstrictive) effects of the drugs.

On the other hand, inhaled corticosteroids can significantly reduce the risk of tolerance to beta-agonists when used in combination therapy.

Antihistamines

Researchers are not sure why antihistamines stop working. Most evidence shows that drug tolerance does not happen no matter how long or aggressively the medications are used. If anything, prolonged use tends to reduce a person's tolerance to the side effects of these drugs (like drowsiness).

There are still many claims that the effects of antihistamines can wane. More often than not, these diminishing effects are related more to the natural course of a person's allergy than to the drug treatment.

For many people with allergies, a mild hypersensitive reaction can get worse over time, particularly with certain food allergies or cross-reactive responses that are vulnerable to multiple allergy triggers (allergens).

What to Do If Your Allergy Meds Stop Working

If your allergy medications aren't working anymore, the first step is to call your provider. They can help figure out why this may be the case and recommend what to do next.

Your healthcare provider may recommend one or more of the following:

• A new treatment: This may mean switching to a different medication or adding one to your current treatment plan. For example, maybe your symptoms now require prescription-strength medication instead of an OTC one. Or maybe you need a drug that treats nasal congestion that you never experienced before.
• A higher dose of your current medication: The drug you are using may still be effective for you—you may just need more of it. Never up the dose of a prescription drug without talking to your provider. If using an OTC product, stick to the dosing schedule on the label unless your provider instructs you otherwise.
• Taking a drug holiday: This is a break from your medication to remove the substance from your body for a while. You can then start taking it again by altering its use with another treatment to prevent tolerance from building up again.

Certain other health conditions can affect how effective your allergy treatment is as well. With that, your healthcare provider may also:

• Add/change treatment for complicating health conditions: Having an underlying medical condition like asthma can make your allergy symptoms harder to control. If you get recurrent or severe asthma attacks, your provider will probably prescribe you a combination inhalant like Advair or Symbicort, which has both a LABA and a corticosteroid drug.
• Evaluate you for other conditions: If you've been consistently using allergy treatments but your symptoms are not getting better, you are getting worse, or have new symptoms, you may not have allergies after all. For example, congestion and sneezing can also be due to nonallergic rhinitis. A cough that won't go away can also be a symptom of gastroesophageal reflux disease (GERD).

Summary

If you overuse certain allergy medications or use them for a long time, it is possible to build up a drug tolerance. You might be able to overcome it by taking a break from the treatments, then starting up again by alternating between more than one treatment to avoid tolerance in the future.

But there's another possibility: Often when allergy medicine stops working, the problem is that your allergies or symptoms have gotten worse and you need to change your treatment accordingly.

If you're no longer getting the symptom control you once did from your allergy medication, speak to your healthcare provider.