I got this reaction too! I'm a teenager and had never had sweating problems before. I went on a website concerned about the sweating when one post included Zyrtec in it. So i looked further into this and I think it is the zyrtec! I have been taking Zyrtec or Zyrtec-D every day for 2-3 years and that's when the sweating began. Sweating is listed in a 2-3% of people in a study but not listed as the common side effects. I've also experienced weight gain but not sure if it's related yet. Does anyone else who takes Zyrtec feel like their body temp. is also off? like when others are hot your cold and vise versa?

1) "Cetirizine is an effective agent in the treatment of Kimura's disease, which mostly occurs in young Asian men, affecting the lymph nodes and soft tissue of the head and neck in the form of tumor-like lesions. Cetirizine's properties of being effective both in the treatment of pruritus and as an anti-inflammatory agent make it suitable for the treatment of the pruritus associated with these lesions. In a 2005 study, the American College of Rheumatology conducted treatments initially using prednisone, followed by steroid dosages and azathioprine, omeprazole, and calcium and vitamin D supplements over the course of two years. The skin condition of the patient began to improve and the skin lesions lessened. However, there were symptoms of cushingoid and hirsutism observed before the patient was removed from the courses of steroids and placed on 10mg/day of cetirizine to prevent skin lesions;[4]an agent suitable for the treatment of pruritus associated with such lesions. Asymptomatically, the patient's skin lesions disappeared after treatment with cetirizine, blood eosinophil counts became normal, corticosteroid effects were resolved, and a remission began within a period 2 months. It is also thought that the inhibition of eosinophils may be the key to treatment of Kimura's disease due to the role of eosinophils, rather than other cells with regards to the lesions of the skin."
Source and further information:
http://en.wikipedia.org/wiki/Zyrtec


2) "Zyrtec is an antihistamine that reduces the natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose.

Zyrtec is used to treat cold or allergy symptoms such as sneezing, itching, watery eyes, or runny nose.

Zyrtec is also used to treat itching and swelling caused by chronic urticaria (hives).

Zyrtec may also be used for other purposes not listed in this medication guide."
Source and further information:
http://www.drugs.com/zyrtec.html

Further information:
http://www.webmd.com/.../...+ORAL+TABLET.aspx
http://www.medicinenet.com/cetirizine/article.htm
http://pediatrics.about.com/.../05_zyrtec.htm

---- ADDED SWEATING SYMPTOMS -------
I did not find sweating in the listed side effects of Zyrtec. However, this symptom appears in several patient reports:

"after the 4th day starting getting severe muscle & joint pain. Then starting sweating nonstop followed by cold chills ongoing for 48hrs straight. Stopped taking the Zyrtec and now I have hives which from reading others reports is part of the withdraw. Do not take this drug."

"I started taking the Zyrtec in December, and within 60 days gained 20 pounds. I was told I had simply reached 'that age'. While taking the Zyrtec non-stop over the year - the weight continued to add on at about 1 pound per month after I was told that Zyrtec could increase appetite. So - the increase continued even though I was re-doubling my efforts to change. Prior to taking this medication, I have NEVER had any problems with weight...EVER. And since taking it, even life-style changes in diet and exercise have had no impact. I find that shocking for someone who NEVER exercised to be able to get nothing out of it at all. It's counter intuitive, to say the least. I also experienced other side effects, which may also have resulted from the weight gain - I sweat ALL the time. I never used to sweat very much at all."

"Muscle twitching especially in the feet and jumping during sleep. Anxiety to the extent of breaking out in a sweat. Depression, strange thoughts, moodiness. Sleepiness during the day."
Source and further information:
http://www.askapatient.com/viewrating.asp

"Q: My daughter (12 yrs old) has Hashimoto's and takes 100mcg Synthroid. She was diagnosed about 4 years ago. This past year she is experiencing excessive underarm sweating (she's probably about 1/2 way or more through puberty). I'm trying to figure out what is causing it (it's more than "normal" because her fraternal twin sister does not have the same problem). She takes Synthroid, Advair 100/50 and as needed Zyrtec, and Aleve (for spondyloarthropathy). Any idea if the Sweating - absent could be caused by the thyroid.
We're due for a TSH next month to see if the meds are still on track; Hands and feet are still freezing.

R. You are describing excessive sweating in a patient with hypothyroidism. The only way to see if she is affected by her treatment is as you suspected, checking a level, tsh but also a free T4, if those are normal I would think that this is unrelated. I have a few patients with hyperhidrosis, which is excessive sweating of watery sweat -not stinky kind. It is an excess autonomic phenomenon where the sweat glands are very sensitive to stress etc. and the body will sweat. Some dermatologists prescribe strong prescription strength deodorant/antiperspirants and others have used even Botox injections. If her levels are normal I would ask if it is extreme enough for her, then if she is really bothered by the sweating see a dermatologist."
Source and further information:
http://www.medhelp.org/posts/show/401608

.

I find that allergy shots are not always effective in treating allergy conditions. They are injecting the antigen into your body causing an allergic response in order to build up an immunity to the antigen. However it does wreak some havoc on certain cells in the body associated with an allergic response, realesing certain chemical mediators, one of them being histamine which is why we take anti-histamines when we get the itchy, watery eye thing going. But some people do not get any relief from this. My daughter was on allergy shots for asthma, however her asthma was not triggered by allergic reactions but rather from accquiring a respiratory infection (known as intrinistic asthma), so I took her off of them. I have had injections myself along with being on zyrtec and no matter what I do I cannot get relief from this therapy. I have kind of learned to just suffer with it and to take an anti-histamine like Benedryl and psuedoephidrine for nasal congestion. It works better than the other therapy for me and is alot easier on my pocket book.