Many experts expect the trend to continue, as the Bank of Japan and European Central bank expand their easing programs, while the Federal Reserve shrinks its stimulus.

The currency moves can hurt U.S. investors, Tom Lydon, editor of ETF Trends, tells Yahoo Finance. Though foreign stocks have rallied on news of the additional easing, the falling yen and euro lessen the value of Japanese and European stocks in dollar terms.

"Even if [foreign] equities maintain [their gains], the currency conversion can be really devastating, and many of us have not seen that for decades," Lydon said.

So how can investors protect themselves? Consider WisdomTree’s Europe Hedged Equity ETF (Ticker: HEDJ) and the Deutsche X-Trackers MSCI Japan Hedged Equity ETF (DBJP), Lydon says. As the names suggest, both funds hedge their currency exposure.

If you want to profit on a rising dollar, consider PowerShares DB US Dollar Bullish ETF (UUP), Lydon says.

As for the yen, "it’s still the divergent-growth, divergent-policy story," Robert Sinche, global strategist at Amherst Pierpont Securities, told Bloomberg. Japan's economy shrank 1.6 percent annualized in the third quarter.

"We are seeing capital flows out of Japan, both official and unofficial, and I think that continues this movement down in the yen," he said.

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