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Are blood tests for allergies more effective than skin/scratch tests?

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Internal Medicine Specialist
Practicing since : 1980
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Hello...are the blood tests for allergies more effective than skin/scratch testing? I am 56 year old female with collagenous colitis and recently developed allergy type symptoms to many foods, cats and the sun. After about thirty minutes of exposure, a red raised and itchy rash develops on all skin surfaces exposed to the sun. I had blood testing for allergies that my FP doc told me "would check for everything" and the results showed an allergy to a tropical grass.
Posted Thu, 14 Nov 2013 in Asthma and Allergy
Answered by Dr. Rakesh Karanwal 57 minutes later
Brief Answer:
Blood test for allergies is superior to skin tests

Detailed Answer:
Hi Mrs. XXXX,

Thanks for your query.

Firstly, blood test for allergies is much superior to skin/scratch tests.

Further, in the presence of collagenous colitis, intolerance to certain foods- such as seafood, peanuts, cow's milk, chocolates, beverages, eggs, wheat, barley, rye or soy- can be mistaken as food allergies. Both conditions manifest with nausea, vomiting, abdominal cramps/discomfort, diarrhea etc..

Also, asthma and wheezing, sudden onset of sneezing, nasal flow, irritation in throat and eyes, are due to allergy.

As you have been detected as allergic to tropical grass, allergic reaction to cats and horses (which move around outside the house in grassy terrains) is understandable.

But, extreme photosensitivity does not exactly fit in the category of allergic disorders. Allergic disorders with hypersensitivity to sun may point to an autoimmune condition called Lupus (Systemic Lupus Erythematosis) or Porphyria.

Consult your doctor and discuss my suspicion of the possibility of SLE/Porphyria. He will know what investigations need to be carried out and, depending on the outcome of the tests, prescribe specific treatment.

Hope I have answered your query. In case of more clarifications, I will be glad to answer.

Fond regards,

Dr. Rakesh Karanwal
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