More and more people are adding honey into their everyday diet, and particularly using it as a natural sweetener for tea or coffee. When you consider that honey has many antibacterial and antifungal properties it is easy to see why.
It has recently been discovered that in the process of the enzymes in the bees honey stomach breaking down the glucose from the nectar, that hydrogen peroxide is created which is what gives most raw honey antibacterial properties. Some pollens negates this effect a little but for the most part, most quality raw honey contains hydrogen peroxide. Honey is also extremely low in water and highly acidic, both conditions are a hostile environment for bacteria. So that's why most honey is considered antibacterial.
The reason why raw manuka honey is hailed as the high antibacterial honey is because in addition to the hydrogen peroxide which comes from the bees enzymes, manuka honey also contains an additional and much stronger antibacterial component that comes specifically from the manuka flower. This type of antibacterial activity is called non-peroxide activity or NPA for short. The non-peroxide activity of manuka honey is made up of three components: Methygloxal (or MG for short), dihydroxyacetone (DHA) and Leptosperin.
The reason why you've been told not to have honey in your hot tea is because hydrogen peroxide, the antibacterial component of most quality raw honeys does die in heat and light. So yes, most honey, in a cup of hot water will lose it's antibacterial qualities.
NPA which is unique to manuka honey is both heat and light stable - meaning the special, high antibacterial properties of manuka honey don't die in tea the same way that hydrogen peroxide found in other honey does. Hence, manuka honey is the ideal and natural drinking honey.