Skin Allergies: Causes and Treatment for Rash Expansion

Redness and swelling due to allergic reaction spreading?

Hello, doctor.
About 10 days ago, I suddenly noticed two spots on my left calf that looked like moles, but upon closer inspection, they appeared slightly raised like small blisters, with some mild redness around the skin.
I foolishly popped them, and it was like the blisters had burst.
After that, I applied a hydrocolloid dressing to protect the wound.
Four days ago, I realized that I hadn’t changed the dressing for too many days, which caused the adhesive area to become red, swollen, and itchy due to an allergic reaction.
After applying an anti-itch cream, I noticed the allergic area had expanded the next day, and there were several small red bumps around it that looked like insect bites.
There were also some clustered together behind my knee, and it was very itchy.
Initially, I scratched, which caused some to form small blisters.
The next day, a few more appeared not far from the affected area.
My right foot had one that later developed a blister, which accidentally burst.
After it burst, I noticed another swollen bump nearby that looked like a bite, and the two areas merged into one larger red, swollen allergic reaction.
I would like to ask the doctor what might have caused this.
Are the original two black blisters related to this spreading, or could it purely be due to insect bites? (I haven’t been in any grass or woods; it just worsened after I woke up the next day.) I went to the outpatient clinic today and received medication and ointment, but I forgot to ask about the cause due to my carelessness, which makes me feel quite frustrated.
Therefore, I am reaching out to you for help.
Thank you!

Ey, 20~29 year old female. Ask Date: 2016/06/28

Dr. Wu Yuxin reply Dermatology

Without actually seeing the lesion, it is impossible to make a definitive diagnosis.
If it is causing significant distress, please seek medical attention promptly.

Reply Date: 2016/06/28

More Info

Skin allergies, particularly those that manifest as rashes, can be quite perplexing and uncomfortable. Based on your description, it seems that you are experiencing a series of skin reactions that may have originated from an initial irritation or injury, which then escalated due to scratching and possibly an allergic response.

Possible Causes of Your Skin Condition
1. Initial Irritation: The two spots you initially noticed on your calf could have been caused by a variety of factors, including insect bites, contact dermatitis (reaction to a substance that has touched your skin), or even a mild infection. The fact that they resembled small blisters suggests that they might have been vesicular lesions, which can occur in allergic reactions or infections.

2. Scratching and Secondary Infection: When you scratched the initial lesions, you may have introduced bacteria into the area, leading to further irritation and possibly a secondary infection. This is common when the skin barrier is compromised, as scratching can break the skin and allow pathogens to enter.

3. Allergic Reaction: The expansion of the rash and the appearance of new red bumps could indicate an allergic reaction. This could be due to a variety of allergens, including topical medications (like the anti-itch cream you applied), materials in the artificial skin, or even environmental factors.

4. Contact Dermatitis: If the artificial skin or any topical treatment you used contained allergens, it could have triggered a contact dermatitis reaction, leading to the redness and swelling you observed.
5. Insect Bites: Although you mentioned not having been in areas where you might encounter insects, it’s still possible that you were bitten by a mosquito or another insect while you were sleeping, which could explain the sudden appearance of the rash.

Treatment and Management
1. Avoid Scratching: It’s crucial to avoid scratching the affected areas, as this can exacerbate the condition and lead to further complications, including infection.

2. Topical Treatments: Continue using the topical medications prescribed by your doctor. Corticosteroid creams can help reduce inflammation and itching. If you have been prescribed antihistamines, they can also help manage allergic reactions.

3. Keep the Area Clean: Ensure that the affected area is kept clean and dry. Change any dressings regularly to prevent moisture buildup, which can worsen irritation.

4. Moisturizers: Applying a gentle, fragrance-free moisturizer can help soothe the skin and restore the skin barrier, especially if the skin is dry or peeling.

5. Consult a Dermatologist: If the rash continues to spread or does not improve with over-the-counter treatments, it would be wise to follow up with a dermatologist. They may perform a patch test to identify specific allergens or prescribe stronger medications if necessary.

6. Monitor for Signs of Infection: If you notice increased redness, warmth, swelling, or pus, these could be signs of an infection, and you should seek medical attention promptly.

Conclusion
In summary, your condition appears to be a combination of an initial skin irritation that has been exacerbated by scratching and possibly an allergic reaction. It’s essential to manage the symptoms carefully and avoid further irritation. If the situation does not improve, or if it worsens, seeking further medical advice is crucial. Skin conditions can be complex, and a healthcare professional can provide tailored advice and treatment options based on a thorough examination.

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