Small white balls have been washing up on a stretch of coastline from West Worthing to Brooklands.
According to Worthing Borough Council, they are likely to be natural emulsified oils and organic matter, which are commonly washed up on beaches following stormy sea weather.
They also said there is a possibility they will begin washing up on beaches in Adur.
A council spokeswoman said: “As a precaution Adur and Worthing councils are advising people not to touch the items or allow pets to eat them.
“Both councils will continue to monitor the situation over the coming week. The beaches remain open as usual.”