Synthroid or levothyroxine can make people living with hypothyroidism feel much better, however, allergic reactions or drug sensitivities may occur due to ingredients such as acacia, lactose, and corn starch.
Symptoms ranging from a runny nose to a rash and/or hives, and abdominal pain can occur, and it may take a while to realize that the medication is responsible rather than something else. Hypersensitivity reactions to Synthroid are more common among those with allergies, hay fever, or asthma.
An allergic reaction to Synthroid is most often diagnosed based on history, although allergy tests are available for acacia. Management of this problem most often includes switching to another brand of levothyroxine, and fortunately there are other brands of the drug with different ingredients that can be effective.
Allergens in Synthroid
In addition to the active ingredient, in this case thyroid hormone, most medications also contain inactive ingredients, known as excipients. While these ingredients are inactive, they are not necessarily inert and may cause allergic reactions or other symptoms.
Many allergic reactions and sensitivities to Synthroid are related to acacia, lactose, or corn starch, although allergic reactions to levothyroxine have been reported very rarely.
Acacia is a family of shrubs and trees, and is used as an ingredient (acacia gum) in some medications, including Synthroid brand levothyroxine, to give shape and structure to tablets.
Some people who have allergies to pollen and hay fever, especially tree and grass pollens (such as rye grass pollen), may also have an allergy to acacia, even when it is an ingredient in a medication.
People who have asthma are also more likely to be allergic. For some people with hypothyroidism who have these allergies, taking Synthroid can cause allergic symptoms.
Interestingly, it also appears that people who have seasonal allergies may find that they don’t respond well to their Synthroid during allergy season.
Studies looking at the incidence of sensitivity to acacia are few, but there appears to be a particularly high rate of sensitization among people living in Iran and neighboring countries, as well as the Philippines.
Another ingredient in Synthroid is lactose, which can trigger symptoms in people with lactose intolerance. Lactose intolerance is an inability to digest lactose, the main sugar found in milk.
Lactose is also an ingredient in some foods and medications. Signs of lactose intolerance can include abdominal pain, cramps, bloating, gas, nausea, and diarrhea.
When lactose intolerance is present, these symptoms often begin 30 minutes to two hours after taking Synthroid
Besides acacia and lactose, one of the most common fillers used in Synthroid is confectioners’ sugar (powdered sugar), which contains cornstarch.
Some studies have found that corn proteins cross-react with gluten, which could trigger an immune system reaction to fillers in the same way it does to gluten. Cornstarch can also be a problem for those with a corn allergy.
While this cross-reactivity can occur and affect people with celiac disease or non-celiac gluten sensitivity, gluten itself does not appear to be a problem. A 2017 study looked specifically at the gluten content of Synthroid tablets.
The level of gluten in Synthroid was found to be below detectable levels (by FDA criteria, Synthroid would be considered gluten-free).
And the researchers felt that while the gluten threshold needed to cause celiac disease to worsen is unknown, Synthroid is unlikely to exacerbate symptoms in people with celiac disease.
Signs and symptoms of allergic reactions to Synthroid
Signs and symptoms of an allergy or hypersensitivity to Synthroid can take several forms.
In the case of acacia allergy, symptoms often include runny nose, eye discharge, and congestion, although mood swings can also occur. Some people develop an eczematous-type rash, hives, or generalized itching.
With lactose intolerance, the most common symptoms are abdominal discomfort, bloating, gas, nausea and vomiting.
The signs of a cornstarch allergy may depend on the underlying sensitivity. When there is a corn allergy, symptoms can range from hives to hay fever to anaphylaxis.
For celiac disease, symptoms may suggest an intolerance, such as bloating, abdominal pain or constipationbut can also include less common symptoms ranging from anemia to infertility.
Some people have recognized that they have an allergy by noticing that their Synthroid doesn’t seem to work as well at certain times of the year, for example during hay fever season. If your TSH fluctuates from high to low, there are many potential causes, and hypersensitivity to Synthroid may be one of them.
Although allergic reactions to Synthroid are rare, any allergic reaction has the potential to be life-threatening. You should seek immediate medical attention if you develop dizziness, shortness of breath, wheezing, chest pain, or other signs of anaphylaxis (a serious allergic reaction).
Diagnosis of this type of allergies
Diagnosing an allergic reaction or sensitivity to Synthroid can be challenging, as many people who have these allergies also have hay fever, lactose intolerance, or gluten sensitivity.
Most often, the diagnosis is made by taking a careful history of symptoms, including how they relate to timing of Synthroid dosing, meals, and exposure to other allergens.
If you are concerned that you may have an allergy to Synthroid, it may help to keep a diary of your symptoms. Be sure to document any symptoms of hay fever, hives or itching, and digestive system symptoms you have, as well as how you feel in general.
An allergy can cause TSH levels to rise (and thus hypothyroid symptoms), but there are many possible causes if your thyroid medication isn’t working.
Allergy tests are available for acacia, although allergy may be suspected in those who have previously been diagnosed with allergies to trees or herbs.
There are several tests you can have if you suspect you have lactose intolerance, such as a lactose tolerance test, a hydrogen breath test, or, in children, a stool acidity test.
That said, many people find out about their intolerance on their own, and often the best way to diagnose the condition along with any other food intolerance is to go on an elimination diet.
The same goes for corn allergy, for which skin and blood tests are available but often inaccurate.
If the Synthroid you’re ingesting is a gluten trigger, perhaps the easiest way to determine is to try a different brand of levothyroxine (under the direction of a doctor).
Management and treatment of allergies to Synthroid
If you suspect that you are sensitive to the acacia, lactose, corn, or possibly a gluten trigger in your Synthroid, it is important to notify your healthcare provider. What he will recommend depends, in large part, on the severity of the reaction you are experiencing.
1. For mild symptoms or uncertain allergies
If your symptoms are mild, you may want to continue medication and keep a symptom diary, using allergy medications as needed to control your symptoms until you have a better idea of whether you really have a problem with Synthroid or No.
In case of lactose intolerance, there is also the option of using lactase supplements (which contain the enzyme needed to break down lactose), if you do not want to change your medication. However, lactase supplements themselves can trigger allergic reactions in some people.
two. Switch brands of thyroxine
While you should generally stay on the same brand of levothyroxine to best treat your hypothyroidism, switching to a different brand may not only relieve your symptoms but confirm a possible allergy.
Before switching medications, talk to your doctor and make sure you need to continue thyroid replacement (most people will, but not all).
Levoxyl and Tirosint are brand names of levothyroxine that are free of acacia and lactose. Tirosint appears to be particularly effective in treating people who have celiac disease in addition to hypothyroidism, as it has fewer active ingredients. However, it can cause heart problems, as well as difficulties controlling blood sugar in people with diabetes.
There are also other brands of levothyroxine such as Levothroid and Unithroid. In addition, there are many brands of generic levothyroxine, although there has been some controversy over the equivalence of these products.
Oral desensitization, or allergy immunotherapy (building a tolerance to medication as with allergy shots), is not commonly used when an allergy to Synthroid is diagnosed, but has been effective for some people who appear to have a true allergy to levothyroxine