Procter & Gamble Co. and Philip Morris International Inc. found a common culprit for weaker financial results in recent weeks: changes in currency values.

P&G, the world's largest consumer products company, had initially been counting on foreign exchange to bolster results this year. Instead, Chief Executive Officer Robert McDonald told investors last month it's turned into “a strong headwind” that may have cut about $3 billion in revenue and at least $400 million in profit from previous projections.

The currency blame game is just beginning with second-quarter earnings reports kicking off this week. Members in the Standard & Poor's 500 Index are forecast to end 10 straight quarters of profit gains and report a 1.8 percent profit decline on average, according to data compiled by Bloomberg.