That's pretty good advice, but be careful with taking Piriton Anti-histamine tablets, they definitely make you drowsy.
They are banned by my Company's Occupational Health Doctors for that reason.
I have to deal with medications at work for my staff, who all work in safety critical jobs.
There are plenty of good alternatives, over the counter, which are much, much better.
I personally take one called Fexofenadine 120mg, the generic name, it's very effective and non-drowsy.
I have never been bitten
This and other brand name ones work well.
You do as richnsare say, need to take them for around 2 weeks as they rely on building up in your body, and they don't work like asprin etc, by taking one as required.