Abstract: The reason why adverb dou can license Chinese polarity items including wh-phrases to its left but not to its right has yet to receive sufficient attention in the literature. The existing studies all take it as a Chinese specific phenomenon and constituting a potential problem to the downward entailment (DE) approach to polarity items. This paper, however, argues against this view. We claim that the crucial licensing condition for Chinese polarity items in sentences with adverb dou is the same as that in English, namely that polarity items are licensed by the DE property of the sentences containing them. Under the universal quantification view of dou with its restriction downward entailing and its nuclear scope upward entailing, we can provide a natural account of the fact that dou sentences only license polarity items to its left not to its right, as only the part to the left functions as the restriction of the universal quantifier dou, consistent with the DE approach. The dou as a universal quantifier analysis not only allows us to account for the co-occurrence of dou and polarity items in Mandarin Chinese under the DE approach, but it also provides strong support for the DE approach to polarity items cross-linguistically.