It’s difficult to say what an urticaria patient should avoid, because there are a lot of different types of urticaria, and not all disease characteristics are shared by all patients.

There is a global consensus about substances or situations that may worsen an urticaria episode, increasing itchiness and/or redness. Or, also, substances that can trigger more severe episodes.

An increased body temperature may worsen the symptoms of urticaria. One tip is to avoid situations that could lead to this, such as stress, hot weather, and alcoholic beverages.

There are also substances that can trigger a more serious situation:

• Yellow tartrazine color (FD&C yellow 5) –this is an artificial yellow color found in processed food and in some drugs. It is used to produce the yellow, orange, green, and red colors. It may rarely cause or worsen an urticaria episode in susceptible individuals, depending on the amount ingested. This is controversial among researchers.
• Non-steroidal anti-inflammatory drug – these can worsen or trigger serious urticaria and/or angioedema cases in genetically susceptible individuals. Some examples of these drugs include: acetylsalicylic acid, ibuprofen, phenylbutazone, indomethacin, diclofenac, naproxen, ketoprofen, piroxicam, nimesulid, among others. If you have urticaria and don’t know if these drugs trigger flares, use them only if prescribed by a healthcare professional and after telling him/her that you have the condition.

References:
J Allergy Clin Immunol Pract. 2014 Mar-Apr;2(2):168-71
J Allergy Clin Immunol. 2015 Aug;136(2):245-5