Companies are already complaining about Brexit hurting their business

When S&P 500 companies hold conference calls after quarterly earnings, they are typically a time to update investors on the health of the business and allow analysts to ask questions to get a deeper understanding of the future of the firm.

Conference calls also give executives time to vent about how outside events are impacting their business. Highlighting those events is a valuable way for executives to reassure investors about either the resiliency of the business or how there may be a drag on future earnings.

Currently, it appears that one of the biggest issues on executives' minds is the UK's vote to leave the European Union, or Brexit.

According to FactSet, around half of the S&P 500 companies that have held calls following the vote on June 23 have mentioned the Brexit vote in some way.

"Of the 13 S&P 500 companies that have reported earnings after the results of the 'Brexit' vote were announced (after June 23), 6 discussed 'Brexit' or 'UK referendum' during their earnings conference calls," wrote John Butters of FactSet.

While Brexit probably doesn't pose the biggest risk to these firms, currency impacts have been the biggest complaint of S&P 500 firms for the past few quarters, and Brexit plays into that worry. Additionally, as the hottest topic in the global economy right now, analysts will be more likely to ask questions related to the vote.

So far, companies have been mixed in their reaction to the vote. Here's Butters' breakdown from a note on Friday:

"Two of these companies (Paychex and Constellation Brands) stated they expected to see little to no impact from the 'Brexit' vote. Two other companies (Acuity Brands & Walgreens Boots Alliance) stated that the 'Brexit' vote created 'uncertainty' and 'volatility' in global markets, but did not discuss a specific negative impact on their businesses going forward. The final two companies, Carnival and McCormick & Company, stated that the 'Brexit' vote created unfavorable currency exchange rates which would have a negative impact on their future earnings."

With earnings season kicking off Monday when Alcoa reports results, factors such as Brexit will continue to be on the top of executives' minds either as an excuse for poor results or a legitimate concern for those countries more exposed to the UK.

Either way, Brexit as a concern is probably not going away anytime soon.