The simple and direct answer is because of toxic and the solution is detoxification 

*WHAT IS DETOXIFICATION*

Basically, detoxification means cleansing the blood.
This is done by removing impurities from the blood in the liver,
where toxins are processed for elimination.

The body also eliminates toxins through the kidneys,
intestines, lungs, lymphatic system, and skin.


*Why Do you need To Detoxify?*

YOU need detoxification because in our daily activities,
You battle with free radicals in the air that carry bacteria
and toxins which are very dangerous to the body.

For instance, the food we eat is grown with fertilizer,
the air we breathe is polluted with exhaust fumes and
industrial gases, the water is chemically treated and
the soaps and creams we use all work against our immunity.

Hence, detoxification is the answer, in order to get out all
the toxins in our body.

To prevent cancer, diabetes, high blood pressure,
cardiovascular problems, infertility, bad eyesight and
many other health related problems.


*To prove how healthy you are, read the following below:*

*After using the toilet, observe the following and
see why you need detoxification*

_1. Colour:The colour of your stool must be golden brown.

_2. Size and Shape:It should be like a banana in shape not noodle shaped or like that of a goat or cow.

_3. Period:You should not spend more than two to three minutes in the toilet.

_4. Floating:Faeces must be floating on the water, it should not sink immediately.

_5. Stickiness:It must not be sticky.

_6. Frequency:You must go to the toilet at least 1-2times a day

*NOTE:* Anything contrary to one or all of the above shows that
there is a problem or a problem is on the way,
meaning you need to detoxify as soon as 
possible.

*Benefits of Detoxification*

* It Rejuvenates You:* Makes you look younger, prettier and more handsome

*Removes Blood Lipids:* It sheds unwanted materials from your body 

*Reduces Overweight:* It makes you lighter and healthier

*Sexual Performance:* It enhances the performance of male reproductive organ

*Malaria, Typhoid and Migraine:* It is anti-malaria, typhoid and headaches 

*Cholesterols, Viscosity and Blood Fats Removal:* It eliminates cholesterol
and blood fats from the blood vessels, arteries and heart, hence, allowing
free flow of blood to all parts of the human body

*Assists High Blood Pressure Patients:* It is good for high blood pressure
patients to clear the blood vessels path ways

*Bareness or Blocked Fallopian Tube:* It provide solution to the problems
of people desiring children 

*Eliminates Early Menopause:* Assists women not to enter menopause before they are 55 years old 
*Irregular Menstruation:* Assists in eliminating menstrual disorderliness 

*Smooth Digestion:* It eliminates disorderliness in the digestive process 

*Remove Fibroid:* It is used in fighting fibroid 

*It Aids Longevity:* It is beneficial for everyone who wishes to live

*Frequency (Period Per Annum):* It is recommended that everybody must detoxify at
least four (4) times a year i.e. quarterly (every three months)

*It aid medication to work effectively: *It make any drug you take to be absorb easily

Source :
http://drexpert.info/body-detoxification