The invention provides a novel herbal composition containing the extracts of the leaves and / or stem of <italic>Argemone mexicana < / highlight>
plant, optionally containing the extracts of the fruits of <italic>
Cuminum cyminum< / highlight>, which exhibits useful 
in vitro, 
in vivo and interesting immunological and pharmacological activities; a process for preparation thereof; and a method of treatment of 
psoriasis and related immunological and biological disorders by administration of the said novel herbal composition. The useful 
in vitro, 
in vivo and interesting immunological and pharmacological activities exhibited by the extracts and fractions of the leaves and / or stem of <italic>Argemone mexicana < / highlight>
plant include 
immunosuppression, lymphoproliferation inhibition, 
cytokine modulation such as IL-2 inhibition, IFNgamma inhibition, IL-10 induction, 
keratinocyte proliferation inhibition, 
keratolytic activity, endothelial 
cell proliferation inhibition, inhibition of 
cell adhesion molecule expression such as ICAM-1, MEST inhibition, and enzymes inhibition such as p60src 
Tyrosine kinase, which are known to be involved in anti-psoriatic activity. The novel herbal composition(s) is useful in the treatment of various disorders, such as 
psoriasis including plaque 
psoriasis, gutatte psoriasis, pustular psoriasis and psoriasis of the nails; dermatitis and scleroderma; eczema; inflammatory disorders and other autoimmune diseases like psoriatic 
arthritis, 
rheumatoid arthritis, Crohn's 
disease, 
multiple sclerosis, 
irritable bowel disease, ankylosing spondilitis, 
systemic lupus erythremetosus and Sjogren'
s syndrome; allergies like 
asthma and chronic obstructive 
pulmonary disease and is safe, well-tolerated, non-toxic, with minimal and reversible adverse reactions or side effects, and most importantly, with minimal relapse or recurrence of the 
disease following completion of a 
treatment regimen. The invention also describes the presence of 
phosphodiesterase (III, IV and V) inhibition and 5-
Lipoxygenase inhibition in the aqueous, ethanolic or aqueous-ethanolic extracts of fruits of <italic>
Cuminum cyminum < / highlight>
plant.