Some people don't even know what's causing these Chinese to cover their noses.
It's Because you're spraying way too much deodorant to cover your body odor. Genetically, Chinese have the lowest occurrence of body odor at only 5%.
For Africans, it's 99.5%, for Europeans, it's 98%. To cover their body odor, foreigners in China bathe themselves in perfume, which is extremely unusual in East Asia and China. Many Chinese find the smell of deodorants jarringly strong.
Some foreigners come to China, bathed in deodorant, thinking they smell nice. And gets offended when people are covering their noses near them.
Without deodorant, you smells bad. With deodorant, the smell gets into our noses and give many of us a headache. We understand it's genetics, for example, when I sweat, it's just water with a bit of sodium, vast majority of Chinese have no smell even when drenched in sweat.
But if you really have to chose between smelling bad or the headache inducing deodorant, dial it slightly towards smelling bad, because body odor does not travel as far as the smell of deodorant.