Hi Helen,
From this site:
http://monroe.ifas.ufl.edu/faq_citrus.htm

"What's causing the leaves of my citrus trees to be curled and crinkled?
Two Possibilities: Citrus Leaf Miner Damage — This insect is the maggot of a tiny fly that lays eggs into the leaves. Maggots hatch from the eggs and "mine" their way through the leaves causing them to cup and crinkle. "Squiggly" lines can also be seen in the affected leaves. This insect is not harmful to the health or fruit production of established trees. Young citrus trees may benefit from sprays of horticulture oil which interfere with the fly's ability to lay eggs into the leaf. Spray each time a new flush of growth appears. Read the label of oil product carefully, as horticulture oil can burn the leaves when applied incorrectly. Leaf Miner Damage

Or Aphid Damage – Curled, distorted leaves can also be the result of aphid insects. These pests have needle-like mouthparts which pierce the leaves and feed on the plant sap. They always feed on the newest, most tender growth. As these leaves mature, they exhibit the damage, but by then the aphids are long-gone. Aphid damage is mostly aesthetic and can be ignored. If aphids are detected, they can be easily controlled by forceful sprays of water or by insecticidal soaps. Aphid damage"

There are environmentally friendly solutions you can use. Visit this site once you have id'd your problem.

http://gardensalive.com/index.asp?bhcd2=1099694162

Newt