A question often asked is "Are tattoos haram in in Islam ?"
The Answer is that permanent Tattoos are Haram in Islam and the Prophet of Allah has cursed the person who has tattoos done on them and the one on whom tattoos are done.
It is narrated that ‘Abd-Allaah ibn Mas’ood (may Allah be pleased with him) said: “May Allah curse the women who do tattoos and those for whom tattoos are done, those who pluck their eyebrows and those who file their teeth for the purpose of beautification and alter the creation of Allah.” (al-Bukhaari, al-Libaas, 5587; Muslim, al-Libaas, 5538).
It was narrated that Abu Juhayfah (may Allah be pleased with him) said: “The Prophet (peace and blessings of Allah be upon him) cursed the one who does tattoos, the one who has a tattoo done, the one who consumes riba (usury or interest) and the one who pays it, and he forbade the price of a dog and the earnings of a prostitute, and he cursed the image-makers.” (Narrated by al-Bukhaari, 5032).
So having tattoos done and tattooing is a major sin. The reason for it being haram has not been given but some scholars believe that it may be because it is changing the creation of Allah.
The curse is not permanent but it is lifted when a person sincerely repents to Allah for this mistake. So one should not feel doomed because they committed this mistake when they were in days of Jahilia (ignorance).
As for things which are not permanent such as henna painting on women's hands , feet and so on, they are not regarded as tattoos and are allowed in Islam.
Many times I received e-mails from non Muslims wishing to become Muslim and from New Muslims who had tattoos done when they were not Muslim. A person can become a Muslim even if they have had tattoos done to them or if they were involved in tattooing. You can do not have to remove them in order to become a Muslim. You can pray, do wudhu and do all your Islamic duties even if you have tattoos. This is because Islam erases all sins that a non Muslim committed before he or she became a Muslim.
“Except those who repent and believe (in Islamic Monotheism), and do righteous deeds; for those, Allah will change their sins into good deeds, and Allah is Oft-Forgiving, Most Merciful”
It was narrated that ‘Amr ibn al-‘Aas said: When Allah put Islam in my heart, I went to the Prophet (peace and blessings of Allah be upon him) and said: “Give me your right hand so that I may give you my oath of allegiance.” So he held out his hand, but I held my hand back. He said, “What is the matter, O ‘Amr?” I said, “I want to make a condition.” He said, “What is your condition?” I said, “That I be forgiven.” He said, “Do you not know that Islam wipes out whatever came before it, and that hijrah (migration for the sake of Allaa) wipes out whatever came before it, and that Hajj wipes out whatever came before it?”
(Narrated by Muslim, 121).
Its is also allowed to remove tattoos using modern medicine such as laser surgery.