Love that turns toxic is neither healthy nor genuine, though the intentions of each partner are often well-meaning.
A couple relationship can be described as toxic when, due to emotional reactivity and defensive reaction patterns, it no longer promotes, and instead harms the mental, emotional and, or physical health, well-being and growth of each partner. The relationship is increasingly off balance, a factor that is affected by and directly affects the individual inner sense of balance, health and safety of each partner.
In contrast, genuine love is an empathic connection that recognizes the authentic other and self as separate and unique beings, even encouraging the individuality of each as essential to the formation of healthy intimacy in a relationship.
Neurological findings in the last decades show that we are wired for certain early protective behaviors in life, and that these can become habitual responses that get automatically activated, as they most often operate without conscious awareness. Intense emotional experiences in childhood can alter the structure of the brain and have enduring effects in adulthood.