Herbalism has a long tradition of use outside of conventional medicine even before recorded history. It is becoming more mainstream as improvements in analysis and quality control along with advances in clinical research show the value of herbal medicine in the treating and preventing inflammatory and other diseases. This focuses the attention on the possibility of the presence of anti-allergic compounds in the extracts of some plants that may help control common allergic diseases including asthma. To test the possible anti-allergic and prophylactic effects of the aqueous extract of Thymus serpyllum L. (Ts) on ovalbumin-induced asthma clinical and hematological parameters in Syrian hamster models