Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your query it seems that itching all over the body along with red dots seems to be due to allergic reaction to some unknown allergen and it seems to be considerably severe allergic reaction.. It can also be due to allergic reaction to Penicillin that is an antibiotic and is a common presentation of antibiotic caused allergy.. In case if the reaction is severe just one dose of anti allergic will not necessarily resolve the problem and you need to take the anti allergics for 3 to 5 days after consulting an Allergist.. Other causes of these symptoms can be Contact Dermatitis, Scabies, Hair follicle infection of Folliculitis etc.. I would suggest you to consult an Allergist and get evaluated and a thorough clinical evaluation and investigations like RAST test, Patch test, food challenge test etc can help in diagnosis and treatment can be done accordingly.. You can be advised anti allergics like Levocetrizine or Allegra, short course of steroids and topical application of steroid ointment, doing cool compresses over the rashes and application of Calamine lotion to soothe the skin.. You can also be advised a Steroid injection initially to relieve the symptoms soon.. In case of Scabies oral Ivermectin and topical application of Premethrin ointmet can help.. In case of folliculitis oral antibiotics and topical antibiotics and steroids can be advised.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora.