Importing decimal numbers from excel as double, not as string

Hi All,
I'm trying to import a large table of chemical data in decimal format with lat/long coordinates from excel in to ArcMap. I have deleted non-numeric characters, saved as CSV and added to arcmap, then displayed XY data and exported to shapefile. However, although columns without decimals have been recognised as numbers, decimal numbers are classified as strings. How do I import them so all fields are classified as double?

Many thanks,
Alex