Exposure to these contaminants can affect health via allergies, infection, mucous membrane and sensory irritation and toxicity--alone or in combination. Often, individuals who are ill from toxic exposures have complex symptoms that include chronic inflammation, neurological problems, vascular or respiratory issues, chronic fatigue, reproductive problems, chronic sinusitis, immune system dysfunction, joint aches and pain, dermatological effects, gastrointestinal tract disturbances, and peripheral and central neuropathy. The brain is also often affected with a condition referred to as "brain fog."