Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query in detail and can very well understand your health concerns..
As per your explanation of symptoms redness and bruising at the site of
bee sting is due to
allergic reaction to the poison left by the bee sting under the skin..
Bruising seems to be due to pricking of any peripheral blood vessel with the bee sting leading to spillage of blood into soft tissues..
Cephalexin is an antibiotic use to treat bacterial infection but in this case you need to take anti-allergics like Zyrtec or Allegra or Benadryl to reduce the allergic reaction..
If there is pain Over the counter painkiller like
Ibuprofen or Advil can be taken..
Apply
Hydrocortisone ointment over the area to reduce local inflammation..
If you can see the bee stinger embedded on the skin get it removed by a doctor or you can remove it yourself as it can release more poison and cause exaggerated allergic reaction..
Do cool compresses over the area..
Hope this information helps..
Thanks and regards..
Dr.Honey Nandwani Arora..