The efficacy of any formulation is linked with the ingredients inside. Almost all legit companies share the ingredient information with the public because they only use the premium ones. If a company is hiding this, it could be an alarming thing, and you should never trust any company that is not transparent in information handling. 

As to Sugar Defender, here is a list of ingredients that go inside. 

Eleuthero

The first ingredient is eleuthero, which improves metabolism while warding off weakness and fatigue in the body. 

Coleus

Coleus improves cellular functions, aids in fat burning, regulates blood circulation, and plays many other helpful roles in the body. 

African Mango

This is a fruit with a high medicinal value. It saves from fat absorption and controls cravings so that the body does not experience erratically high sugar and cholesterol levels. 

Guarana

This plant is native to the Amazon region. In local areas of its growth, it has been widely used in various treatments. It relieves digestive issues, improves cardiac health, and promotes natural weight loss. 

Gymnema

This plant controls appetite, reduces hunger pangs, and saves you from overeating. It also balances digestive hormones and cholesterol levels so that the body can maintain a healthy weight.

Ginseng

Panax Ginseng provides antioxidant support to the body. It also improves brain health and makes you think and focus better while keeping the glucose levels stable. 

Chromium

Finally, the last ingredient is chromium, a mineral that plays a vital role in blood sugar regulation. A daily intake of chromium can prevent the development of metabolic diseases, including obesity. 

These ingredients do not cause any allergy. But people with allergies linked to plant-based ingredients should talk to a doctor first before using any such product.