allergic to phentermine

Am I Allergic To Phentermine?

General Phentermine Questions?
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Listed among the side effects of phentermine are indications of an allergic reaction to the medication. These allergic reactions include skin rashes and itching to the more severe symptoms of swelling and breathing problems. Here we explain the signs of a phentermine allergy and what to do if you start to experience these reactions.

Could I Be Allergic To Phentermine?

As with all medications, there is a possibility that you could be allergic to phentermine. It is difficult to know if you are allergic until you have taken it for the first time. However, previous allergic reactions to certain products increase the likeliness of a phentermine allergy. These include appetite suppressants, food preservatives, dyes, and a range of other medications including ephedrine and metaproterenol. So, if you have a history of allergic reactions to these medications you should inform your doctor before being prescribed phentermine.

An allergic reaction is a sign that your body’s immune system is being triggered by phentermine or one of its ingredients. This can include the active ingredient phentermine HCL or inactive ingredients such as coloring. However, a previous allergic reaction to similar medications or other products does not necessarily mean that you cannot take phentermine. Instead, your doctor might advise you to take a smaller dosage to start with.

Signs Of Allergic Reactions To Phentermine

Mild allergic reactions to phentermine include itchy eyes, a rash, or hives. Depending on the severity of these symptoms, an over-the-counter antihistamine should help to reduce the reaction. However, even if you are able to control a mild reaction to phentermine with antihistamines, you should seek further advice from your doctor. This is because with continued use, allergies can worsen and may result in more severe reactions. Unlike other side effects such as dry mouth or insomnia, allergic reactions are unlikely to reduce over time. In fact, a buildup of phentermine in your system is likely to worsen allergy-related symptoms and could be very dangerous.

A more serious allergic reaction, known as anaphylaxis, can cause swollen lips, an itchy throat and breathing problems. You should stop taking phentermine immediately and speak to your doctor if you experience symptoms like these. Depending on the severity of breathing trouble, taking antihistamines can help to reduce this. However, if symptoms persist then you should call 911 as severe allergic reactions can lead to losing consciousness.

If you have other symptoms, such as pain, then this is most likely a side effect rather than an allergic reaction. However, if you feel symptoms such as pain or tightness in your chest then you should stop phentermine immediately and speak to your doctor; serious side effects like chest pain should not be ignored due to the ways phentermine can affect the heart.

allergic to phentermine

What If I’ve Taken Phentermine Before?

Despite the assumption that allergies appear in childhood and then stay with us for life, allergies can come and go. Just as you may suddenly develop an allergy to cat hair or a certain food, you can have an allergic reaction to a medication you’ve had before. So, even if you’ve taken phentermine before, you may suddenly experience signs of an allergic reaction. You should be just as vigilant as a new phentermine user when it comes to monitoring your side effects and symptoms from your first dose. This is because not only might your immune system have changed, the phentermine could be made by a different manufacturer or using different ingredients.

Could It Be An Allergy To Something Else?

If you change your diet at the same time as starting phentermine then there is a small chance that the reaction could be as a result of a food allergy. For example, it’s becoming more common to switch to non-dairy milks in a bid to lose weight as many people mistakenly see dairy milk as a less healthy option.  However, soy is one of the most common allergy-producing foods. Therefore, suddenly switching to soy milk might produce an allergic reaction if soy is not a product you previously consumed.

Similarly, as mentioned above, you can also develop an allergy to a food you have consumed before. Fish allergies and shellfish allergies are more likely to appear in adults for example. And, since most food allergies result in similar symptoms, such as rashes, itching, swelling and breathing trouble, it is possible to confuse one allergy for another. Under the guidance of your doctor you can check to see if your reaction is as a result of a phentermine allergy by discontinuing use and monitoring your symptoms.


If you are unsure about how your body is reacting to phentermine then you should always speak to your doctor as soon as possible. In the event that you cannot take phentermine then we recommend the alternative Phen Caps. Like phentermine, Phen Caps boost energy and suppress appetite to help you lose weight. However, since Phen Caps contain different ingredients to phentermine, they will not produce the same allergic reaction.

Have you experienced an allergic reaction to phentermine? Let us know by commenting below.

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2 Responses

  1. I started duromine about 3 weeks ago, everything going fine and then one day I woke up with a rash, swollen lips and uncontrollably itchy! I have now that this for 5 days! Antihistamines are slowly working but is not a fast fix! I’m gutterd I can’t take them anymore but it body is telling me to stop so I have!

  2. Anyone know how long a phentermine rash lasts after long term use? Stopped one week ago. Not itchy, just unsightly!

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