PARIS, Aug 29 (Reuters) - French cosmetics group Clarins on Friday reported a drop in first-half net income to 24 million euros ($35.38 million) from 36.7 million euros a year earlier and renewed recent caution about the impact of currency swings.

It confirmed a forecast of 4 percent in annual sales at constant exchange rates, having lowered the target from 4-6 percent at the start of the year.

Clarins said unfavourable currency movements had cut 10.4 million euros from operating profit, which came in at 27.8 million euros, down from 40 million euros, and would continue to have an unfavourable impact on profitability.

Operating profit fell 6.6 percent at constant exchange rates due to promotional costs, weak perfume sales and restructuring costs, Clarins said in a statement.

Revenue rose 4.1 percent at constant exchange rates but fell 1.8 percent at average actual rates to 485.7 million.