I have good news for all you smelly breastfeeders out there (lol) - this includes me!
Your skin is the largest organ your body has, and the largest organ of elimination. (Others being your liver, kidneys, bowel and lungs). Our bodies are so intelligently designed that we eliminate a vast array of toxins from our pores when we sweat. Particularly near our lymph glands under the arms.
Numerous studies have shown that toxic elements that we consume (ie pesticides and heavy metals in food, water and personal care products) end up passing through into our breastmilk. So in order to purify and reduce the amount of toxicity in our breastmilk, our body naturally speeds up this toxin elimination process, by making us sweat more profusely- causing the sudden appearance of unpleasant body odour. This is one of the reasons that breastfeeding has been found to reduce the risk of breast cancer so dramatically; because with each baby that is birthed and breastfed, the woman's body will go through this natural detoxification process, thus reducing the amount of toxicity that her sensitive breast tissue may be exposed to in future.
What you must never do when breastfeeding is use an anti-perspirant, which will block your body's ability to undergo this process efficiently, not to mention expose your body and baby to a range of very toxic chemicals. What you can do however, is wash frequently with an organic or chemical-free soap and use a natural or organic deodorant which will assist in masking the odour, without blocking your pores and preventing detoxification. MiEssence does a good natural deodorant - the most effective I have found so far.
The good news is that the body odour will decrease with time, as you continue to breastfeed. The body odour is likely to be worse if you have been using chemical (ie mainstream) deodorants or antiperspirants for a long time. Hopefully you are able to put up with it long enough to witness the body odour diminish before you cease breastfeeding. Then you know that your body has undergone a thorough cleansing! Once you cease breastfeeding, whatever you do - do not resume using the chemical deodorants - source a good natural one and stick with it. This will ensure you not only smell less if you breastfeed in future, but you will significantly reduce your chances of having breast cancer.
This is the reason saunas are recommended and utilised at detox clinics/ beauty salons etc. Lower rates of cancer also exist in countries where there is humidity all year round, and thus people are able to sweat toxins out frequently. Bikram yoga is another example that emphasises this principle.
I'm a geek! 
