Fixed Drug Eruptions: Symptoms, Causes, and Treatment

Q: Fixed Drug Eruptions: Symptoms, Causes, and Treatment

Hello, regarding your question, here is my response： Based on your description, it seems that you are experiencing an allergic reaction. <br>As for your inquiry about whether an allergy can occur three days after stopping the medication, it is relatively uncommon for this to happ

Fixed drug eruption

Hello, doctor.
Starting from June 22, I have been taking Augmentin 1g (one tablet in the morning and one in the evening) and Flagyl 200mg (two tablets three times a day) due to uterine inflammation.
After completing a seven-day course, I stopped the medication for about three days.
On July 1, I noticed small, itchy lumps near my navel that resembled mosquito bites.
Initially, I thought it was an allergic reaction due to contact with a dirty floor.
However, by the next day, July 2, the condition had not improved; the redness and swelling were increasing, and the small lumps that looked like mosquito bites had merged and spread down to my chest and genital area.
There were also a few spots on my neck, hands, and face, but those areas resolved quickly.
The legs, however, did not improve.
On July 3, the situation worsened; the redness and swelling showed no signs of subsiding.
Although pressing on the area did not cause pain, the itching was so severe that I couldn't eat or sleep, significantly affecting my daily life, so I went to a clinic.
The doctor diagnosed me with "fixed drug eruption," and I was given antihistamines and a topical corticosteroid, which took about three days to improve.

Could it be possible for a drug eruption to appear three days after stopping the medication? Additionally, I searched online for images of "fixed drug eruption," and they all showed lesions with a black ring in the center, but mine look like mosquito bites.
Why is that? Thank you, doctor.

Chen, 20~29 year old female. Ask Date: 2020/07/08

Dr. Zheng Shuwen reply Pharmacology

Hello, regarding your question, here is my response: Based on your description, it seems that you are experiencing an allergic reaction.
As for your inquiry about whether an allergy can occur three days after stopping the medication, it is relatively uncommon for this to happen after discontinuation; however, since each individual's constitution varies, it is difficult to definitively say whether this medication is the cause.

To help you better assess the situation, is this your first time using this medication? Additionally, during the course of your treatment, have there been any significant changes compared to the past, such as changes in climate or diet? Sometimes, age can also influence one's constitution.

In terms of management, aside from consulting a dermatologist, if you seek medical attention elsewhere in the future, you can inform the healthcare providers about your situation to assist them in their medical decision-making.
Regarding drug rashes, dermatologists have more clinical experience, and information available online may not be comprehensive.
Therefore, it is best for a physician to make an accurate assessment at that time.

If you have any further questions, feel free to call during office hours.
Thank you.
Consultation phone number: 03-3698553 #2505.
Office hours: Monday to Tuesday: 08:30-21:30; Wednesday to Friday: 08:30-17:30; Saturday: 08:30-13:30.

Reply Date: 2020/07/08

More Info

Fixed drug eruptions (FDE) are a type of drug-induced skin reaction characterized by the development of well-defined, round lesions that recur at the same site upon re-exposure to the offending medication. Understanding the symptoms, causes, and treatment of FDE is crucial for effective management and prevention.

Symptoms of Fixed Drug Eruptions
The symptoms of FDE typically include:
1. Lesion Appearance: The lesions often appear as round or oval patches that can be red, swollen, and itchy. They may resemble hives or mosquito bites initially, as you described. Over time, these lesions can develop into plaques that may have a darker pigmentation or a central area of necrosis (black center) upon resolution.

2. Location: FDE lesions usually recur at the same site where they appeared previously, which is a hallmark of this condition. However, they can also appear in new locations upon subsequent exposures to the drug.

3. Itching and Discomfort: The lesions are often itchy and can cause significant discomfort, impacting daily activities, as you experienced.

4. Timing: The onset of FDE can vary. While some reactions occur shortly after drug exposure, others may take days to weeks to manifest. In your case, the delay of three days after stopping the medication before the lesions appeared is not uncommon. The immune response can take time to develop, leading to delayed reactions.

Causes of Fixed Drug Eruptions
FDE is primarily caused by a hypersensitivity reaction to certain medications. Common culprits include:
- Antibiotics: Such as penicillins (like Augmentin) and metronidazole (Flagyl).

- Non-steroidal anti-inflammatory drugs (NSAIDs).

- Anticonvulsants and antimalarials.

In your situation, both Augmentin and Flagyl are known to cause FDE in some individuals. The immune system may recognize these drugs as foreign substances, leading to an inflammatory response that manifests as skin lesions.

Treatment of Fixed Drug Eruptions
The treatment for FDE typically involves:
1. Discontinuation of the Offending Drug: The first step is to stop taking the medication that triggered the reaction. In your case, this would mean avoiding Augmentin and Flagyl in the future.

2. Symptomatic Relief: Antihistamines can help alleviate itching and discomfort. Topical corticosteroids, as you received, are effective in reducing inflammation and promoting healing of the lesions.

3. Monitoring and Follow-Up: It is essential to monitor the lesions for improvement and to follow up with a healthcare provider if symptoms persist or worsen.

Clarification on Lesion Appearance
Regarding your observation about the appearance of your lesions compared to typical images of FDE, it is important to note that not all fixed drug eruptions present with the classic "target" appearance (central necrosis with a darker ring). The initial presentation can vary significantly among individuals. Your description of the lesions resembling mosquito bites is consistent with the early stages of an allergic reaction, which can evolve into the more characteristic lesions over time.

In conclusion, while the timing of your symptoms may seem unusual, it is indeed possible for fixed drug eruptions to develop several days after stopping the medication. The variability in lesion appearance is also common, and individual reactions can differ widely. If you have further concerns or experience similar symptoms in the future, it is advisable to consult with a dermatologist or an allergist for a comprehensive evaluation and management plan.

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