This is from a healthy living website:
Chemicals are used to make fibers suitable for spinning and weaving.
A formaldehyde product is often applied to prevent shrinkage. This product is applied with heat so it is trapped in the fiber permanently.
Petrochemical dyes, which pollute waterways, are used for color.
Chemicals are added to make clothing softer, wrinkle-free, fire-retardant, moth-repellant and stain-resistant.
Commonly used chemicals include volatile organic compounds (VOCs) and dioxin-producing bleach.
Nylon and polyester are made from petrochemicals, whose production creates nitrous oxide, a greenhouse gas that is 310 times more potent than carbon dioxide.
Rayon is made from wood pulp that has been treated with chemicals, including caustic soda and sulphuric acid.
Dye fixatives used in fabrics often come from heavy metals and pollute water systems.
Acrylic fabrics are polycrylonitriles, which may be carcinogenic.
Clothing and fabric that is treated with flame-retardant chemicals, such as children's pajamas, emit formaldehyde gas.
This is not to criticize Clarks. This is an inherent issue with nylon and other man-made fabrics. I suggest you hand wash your hammock in the tub and hang to dry. Or, at the very least, hang the hammock (not in the sun) for a few days to off-gas before you sleep in it again.
That being said, your sickness could have been caused by something else, including motion sickness. Either way, I bet you'll end up loving your hammock once you spend more time in it. Most everybody does.
Best of luck to you!